Transcript: YOW! 2013 Philip Wadler - The First Monad Tutorial #YOW

monads.json

[[{"text": "so this is the first monad tutorial", "start": 0.03, "duration": 8.34}, {"text": "these days there are lots of monad", "start": 3.54, "duration": 9.509}, {"text": "tutorials for Scala or Perl or I think", "start": 8.37, "duration": 7.229}, {"text": "that's channel 9 at Microsoft in the", "start": 13.049, "duration": 5.48}, {"text": "bottom corner and one called yet another", "start": 15.599, "duration": 6.151}, {"text": "presentation on loan ads and they have", "start": 18.529, "duration": 5.621}, {"text": "all sorts of complicated diagrams in", "start": 21.75, "duration": 5.15}, {"text": "them so you can point with this thing", "start": 24.15, "duration": 5.67}, {"text": "going what have we got here", "start": 26.9, "duration": 6.79}, {"text": "this is plumbing this is spacesuit this", "start": 29.82, "duration": 8.43}, {"text": "is burritos and this is funny boxes with", "start": 33.69, "duration": 8.04}, {"text": "balls in them but but remember that", "start": 38.25, "duration": 8.149}, {"text": "symbol okay that symbol is important", "start": 41.73, "duration": 4.669}, {"text": "right - you're all computer scientist so", "start": 48.5, "duration": 3.52}, {"text": "you're not scared by funny looking", "start": 50.61, "duration": 6.15}, {"text": "symbols right good actually we're quite", "start": 52.02, "duration": 7.519}, {"text": "are you scared by funny-looking symbols", "start": 56.76, "duration": 11.73}, {"text": "okay and you can get monads in all sorts", "start": 59.539, "duration": 12.821}, {"text": "of languages so you've got Haskell just", "start": 68.49, "duration": 5.46}, {"text": "go for your segments so this is very", "start": 72.36, "duration": 3.299}, {"text": "colorful pointer writing people", "start": 73.95, "duration": 4.08}, {"text": "sometimes get nervous but you don't need", "start": 75.659, "duration": 3.78}, {"text": "to be nervous as long as you're", "start": 78.03, "duration": 5.55}, {"text": "well-behaved and you can see the Haskell", "start": 79.439, "duration": 6.93}, {"text": "logo actually has built into it this air", "start": 83.58, "duration": 4.95}, {"text": "greater than greater than equal sign", "start": 86.369, "duration": 3.661}, {"text": "which is the monad thing as well as", "start": 88.53, "duration": 3.78}, {"text": "having a lambda built into it then we've", "start": 90.03, "duration": 5.82}, {"text": "got closure f-sharp g-sharp Scala Python", "start": 92.31, "duration": 5.28}, {"text": "we've already heard of Perl so there's", "start": 95.85, "duration": 3.78}, {"text": "lots of languages that use these things", "start": 97.59, "duration": 5.55}, {"text": "and a huge number of tutorials many of", "start": 99.63, "duration": 7.04}, {"text": "them based on some weird kind of analogy", "start": 103.14, "duration": 6.78}, {"text": "so here's the thing about this tutorial", "start": 106.67, "duration": 8.199}, {"text": "it will contain zero analogies and you", "start": 109.92, "duration": 6.87}, {"text": "might have heard that monads come from", "start": 114.869, "duration": 5.25}, {"text": "category theory I have a colleague who", "start": 116.79, "duration": 4.939}, {"text": "refers to category theory as", "start": 120.119, "duration": 6.741}, {"text": "intellectual terrorism so if you've been", "start": 121.729, "duration": 7.241}, {"text": "exposed to that kind of terrorism you", "start": 126.86, "duration": 3.849}, {"text": "might be worried but don't worry you", "start": 128.97, "duration": 4.349}, {"text": "need no category theory", "start": 130.709, "duration": 6.81}, {"text": "whatsoever to understand this talk okay", "start": 133.319, "duration": 7.381}, {"text": "all of you have the right background to", "start": 137.519, "duration": 6.75}, {"text": "understand this talk so please if I say", "start": 140.7, "duration": 5.909}, {"text": "something you don't understand raise", "start": 144.269, "duration": 5.881}, {"text": "your hand and ask a question okay I", "start": 146.609, "duration": 5.58}, {"text": "might accidentally forget to explain", "start": 150.15, "duration": 4.41}, {"text": "something you should be able to follow", "start": 152.189, "duration": 5.011}, {"text": "along if you can't please just ask a", "start": 154.56, "duration": 5.16}, {"text": "question if you're embarrassed to ask a", "start": 157.2, "duration": 5.28}, {"text": "question turn to the person next to you", "start": 159.72, "duration": 5.519}, {"text": "and say he just makes it suitable I", "start": 162.48, "duration": 4.289}, {"text": "don't know about puzzles you know about", "start": 165.239, "duration": 3.75}, {"text": "Mosel and maybe they'll say oh yeah", "start": 166.769, "duration": 4.981}, {"text": "whose lives of such and so but probably", "start": 168.989, "duration": 4.711}, {"text": "they'll take no I don't know about foods", "start": 171.75, "duration": 3.569}, {"text": "either and then you can raise your hand", "start": 173.7, "duration": 8.7}, {"text": "and ask okay oh yeah and then we thought", "start": 175.319, "duration": 12.301}, {"text": "of course all the means trapped in monad", "start": 182.4, "duration": 6.57}, {"text": "tutorial please help", "start": 187.62, "duration": 6.649}, {"text": "and the monad tutorials are coming and", "start": 188.97, "duration": 10.109}, {"text": "here is monad man I thought oh this is", "start": 194.269, "duration": 7.21}, {"text": "just something somebody found some", "start": 199.079, "duration": 5.55}, {"text": "superhero with an M on their chest but", "start": 201.479, "duration": 6.781}, {"text": "actually if you look down there you can", "start": 204.629, "duration": 6.92}, {"text": "see he really wanted a is Katie", "start": 208.26, "duration": 3.289}, {"text": "here.thank Katie for monad man a round", "start": 212.239, "duration": 7.53}, {"text": "of applause for KD and monad man", "start": 215.94, "duration": 3.829}, {"text": "and here's a graph of the amount of", "start": 222.58, "duration": 10.45}, {"text": "known monad tutorials and this is just", "start": 228.44, "duration": 6.99}, {"text": "for Haskell okay not any of the other", "start": 233.03, "duration": 4.679}, {"text": "languages and you notice that in the", "start": 235.43, "duration": 5.6}, {"text": "1990s it suddenly goes from zero to one", "start": 237.709, "duration": 9.331}, {"text": "that's the one you're about to see so", "start": 241.03, "duration": 10.17}, {"text": "here it is the first monad tutorial and", "start": 247.04, "duration": 8.52}, {"text": "I need to say maybe just a little bit to", "start": 251.2, "duration": 7.689}, {"text": "motivate why one would want a monad so", "start": 255.56, "duration": 7.88}, {"text": "monads are there we go there's me and", "start": 258.889, "duration": 11.121}, {"text": "I'm facing this tension so um to my", "start": 263.44, "duration": 12.43}, {"text": "right there is a lambda sign how many", "start": 270.01, "duration": 9.52}, {"text": "people recognize the lambda okay now all", "start": 275.87, "duration": 7.019}, {"text": "of you do good you know so I thought", "start": 279.53, "duration": 5.88}, {"text": "those nice silver one here that was made", "start": 282.889, "duration": 4.321}, {"text": "for me as a gift by one of my students", "start": 285.41, "duration": 5.1}, {"text": "so what lambda represents is the lambda", "start": 287.21, "duration": 6.0}, {"text": "calculus and more importantly a nice", "start": 290.51, "duration": 5.64}, {"text": "sound simple theoretical basis for", "start": 293.21, "duration": 5.16}, {"text": "computing that has no side effects", "start": 296.15, "duration": 5.76}, {"text": "whatsoever right normally when somebody", "start": 298.37, "duration": 5.85}, {"text": "explains computing to you the first time", "start": 301.91, "duration": 3.75}, {"text": "they say well there's a variable here", "start": 304.22, "duration": 3.18}, {"text": "and that's a box and you put stuff in", "start": 305.66, "duration": 3.72}, {"text": "the box and immediately you're often", "start": 307.4, "duration": 4.62}, {"text": "analogies lambda calculus can be", "start": 309.38, "duration": 5.28}, {"text": "explained very simply you have a term", "start": 312.02, "duration": 6.33}, {"text": "and it's equal to another term which is", "start": 314.66, "duration": 6.9}, {"text": "equal to another term and everything can", "start": 318.35, "duration": 5.819}, {"text": "be explained by substituting equals for", "start": 321.56, "duration": 5.57}, {"text": "equals and that's it so it's a wonderful", "start": 324.169, "duration": 8.971}, {"text": "simple model of computing and that's", "start": 327.13, "duration": 7.75}, {"text": "what we want to make use of now I know", "start": 333.14, "duration": 3.18}, {"text": "not all of you are convinced by that", "start": 334.88, "duration": 5.7}, {"text": "that's fine but you all will be right", "start": 336.32, "duration": 7.14}, {"text": "this is how the world is moving right", "start": 340.58, "duration": 5.28}, {"text": "twenty years ago nobody is using Haskell", "start": 343.46, "duration": 6.9}, {"text": "these days it's used at major banks the", "start": 345.86, "duration": 6.36}, {"text": "main - Haskell developers our time and", "start": 350.36, "duration": 3.199}, {"text": "Peyton Jones in time and Marlowe", "start": 352.22, "duration": 3.469}, {"text": "they were both at Microsoft Simon", "start": 353.559, "duration": 3.45}, {"text": "Marlowe's just been hired away by", "start": 355.689, "duration": 2.3}, {"text": "Facebook", "start": 357.009, "duration": 3.69}, {"text": "lots of people these days are using", "start": 357.989, "duration": 6.88}, {"text": "functional languages because when", "start": 360.699, "duration": 6.78}, {"text": "there's no side effects the interface to", "start": 364.869, "duration": 4.59}, {"text": "the function tells you everything there", "start": 367.479, "duration": 5.52}, {"text": "is to know and that level of modularity", "start": 369.459, "duration": 8.3}, {"text": "is really helpful in developing programs", "start": 372.999, "duration": 7.13}, {"text": "okay so the great thing is it makes", "start": 377.759, "duration": 6.07}, {"text": "everything completely obvious and that", "start": 380.129, "duration": 5.62}, {"text": "gives you great structuring properties", "start": 383.829, "duration": 4.59}, {"text": "and in particular these days when we", "start": 385.749, "duration": 4.95}, {"text": "want to make things concurrent it's very", "start": 388.419, "duration": 5.34}, {"text": "helpful because if something's making", "start": 390.699, "duration": 5.49}, {"text": "use of assignment and of two concurrent", "start": 393.759, "duration": 3.93}, {"text": "things making use of assignments you", "start": 396.189, "duration": 2.7}, {"text": "have to worry about how those", "start": 397.689, "duration": 3.99}, {"text": "assignments interleave right shared", "start": 398.889, "duration": 6.87}, {"text": "memory is the root of all evil so if", "start": 401.679, "duration": 5.58}, {"text": "you're in a pure functional language", "start": 405.759, "duration": 4.32}, {"text": "there's no assignment it's much easier", "start": 407.259, "duration": 5.49}, {"text": "to get things to work concurrently or in", "start": 410.079, "duration": 6.56}, {"text": "parallel I'm not saying it's easy but", "start": 412.749, "duration": 6.84}, {"text": "I'm saying that by not having to worry", "start": 416.639, "duration": 5.17}, {"text": "about lots of assignment going on you", "start": 419.589, "duration": 4.41}, {"text": "can focus on the real important problems", "start": 421.809, "duration": 5.64}, {"text": "in making something concurrent ok so", "start": 423.999, "duration": 6.3}, {"text": "functional programming there me with my", "start": 427.449, "duration": 6.36}, {"text": "lambda everything is wonderful I'll show", "start": 430.299, "duration": 5.76}, {"text": "you how wonderful right my daughter is", "start": 433.809, "duration": 4.26}, {"text": "old enough it and she now makes stuffed", "start": 436.059, "duration": 4.801}, {"text": "fuzzy toys to give to me rather than me", "start": 438.069, "duration": 4.77}, {"text": "giving them to her this is the land that", "start": 440.86, "duration": 7.229}, {"text": "she gave me okay and it's fuzzy I want", "start": 442.839, "duration": 7.08}, {"text": "you to think about that right lenses are", "start": 448.089, "duration": 5.01}, {"text": "fuzzy comfortable things but they're not", "start": 449.919, "duration": 5.31}, {"text": "scary theory they are your friends you", "start": 453.099, "duration": 4.38}, {"text": "want to cuddle up to them they want to", "start": 455.229, "duration": 6.15}, {"text": "cuddle up to you okay so everything's", "start": 457.479, "duration": 5.06}, {"text": "wonderful", "start": 461.379, "duration": 6.42}, {"text": "so why on my other side am i plagued by", "start": 462.539, "duration": 7.33}, {"text": "these three demons what are these three", "start": 467.799, "duration": 5.43}, {"text": "demons so we've got the the up arrow of", "start": 469.869, "duration": 7.17}, {"text": "exception raising the Kohen equal of", "start": 473.229, "duration": 8.61}, {"text": "assignment the great evil and the curly", "start": 477.039, "duration": 9.84}, {"text": "sheet of output and remember I said two", "start": 481.839, "duration": 5.461}, {"text": "great", "start": 486.879, "duration": 2.82}, {"text": "thing about pure functional programming", "start": 487.3, "duration": 7.01}, {"text": "is it makes it completely obvious", "start": 489.699, "duration": 10.771}, {"text": "everything that's going on but indeed it", "start": 494.31, "duration": 8.56}, {"text": "can sometimes make things painfully", "start": 500.47, "duration": 6.99}, {"text": "obvious right you have a lot of detail", "start": 502.87, "duration": 6.539}, {"text": "in those cases where you actually do", "start": 507.46, "duration": 4.32}, {"text": "need to pass around state and it does", "start": 509.409, "duration": 6.51}, {"text": "happen right passing that around can get", "start": 511.78, "duration": 7.77}, {"text": "a bit painful so there's things for", "start": 515.919, "duration": 5.61}, {"text": "which sometimes you would think yep", "start": 519.55, "duration": 4.109}, {"text": "exception handling is just the thing", "start": 521.529, "duration": 4.591}, {"text": "outputs just the thing assignment is", "start": 523.659, "duration": 4.351}, {"text": "just the thing and when you need them in", "start": 526.12, "duration": 3.63}, {"text": "your in a pure language what you're", "start": 528.01, "duration": 7.35}, {"text": "going to do not Ghostbusters monads okay", "start": 529.75, "duration": 7.98}, {"text": "so that's what we're going to do so", "start": 535.36, "duration": 4.169}, {"text": "you're ready to program we're actually", "start": 537.73, "duration": 3.33}, {"text": "going to do some coding here are you", "start": 539.529, "duration": 5.18}, {"text": "ready to code are you ready to code", "start": 541.06, "duration": 5.969}, {"text": "let's see we'll skip over that from are", "start": 544.709, "duration": 9.88}, {"text": "you ready to code in Haskell how about", "start": 547.029, "duration": 9.3}, {"text": "are you ready to code in Scala", "start": 554.589, "duration": 5.071}, {"text": "oh that's less maybe we should go back", "start": 556.329, "duration": 6.781}, {"text": "to the Haskell talk right so I gave the", "start": 559.66, "duration": 6.81}, {"text": "talk in Haskell last time and lots of", "start": 563.11, "duration": 5.76}, {"text": "people hood and one reason they went is", "start": 566.47, "duration": 4.619}, {"text": "perfectly reasonable which is rewrite", "start": 568.87, "duration": 4.14}, {"text": "function application differently and I", "start": 571.089, "duration": 3.661}, {"text": "even forgot to explain that clearly at", "start": 573.01, "duration": 3.12}, {"text": "the beginning which is why you have to", "start": 574.75, "duration": 3.3}, {"text": "all ask questions if you don't", "start": 576.13, "duration": 3.149}, {"text": "understand I'm not going to blame myself", "start": 578.05, "duration": 3.45}, {"text": "for not explaining nobody in the", "start": 579.279, "duration": 5.701}, {"text": "audience asked who on them yeah no I", "start": 581.5, "duration": 4.829}, {"text": "should have explained it's really my", "start": 584.98, "duration": 5.849}, {"text": "fault but ask anyway so this time around", "start": 586.329, "duration": 6.87}, {"text": "so that function application is written", "start": 590.829, "duration": 3.421}, {"text": "in the style that looks more familiar", "start": 593.199, "duration": 3.241}, {"text": "and I think that actually is very", "start": 594.25, "duration": 5.07}, {"text": "helpful for audiences indeed my new", "start": 596.44, "duration": 5.55}, {"text": "functional language length uses that", "start": 599.32, "duration": 4.86}, {"text": "style of function application so we're", "start": 601.99, "duration": 4.68}, {"text": "going to do it in Scala you can see it", "start": 604.18, "duration": 4.8}, {"text": "in a more familiar way and long the way", "start": 606.67, "duration": 3.96}, {"text": "we'll see some definitions of the word", "start": 608.98, "duration": 5.099}, {"text": "monad so it actually monad noun 1", "start": 610.63, "duration": 7.519}, {"text": "philosophy any fundamental entity", "start": 614.079, "duration": 6.631}, {"text": "especially if autonomous on", "start": 618.149, "duration": 3.731}, {"text": "sure that makes you feel much better", "start": 620.71, "duration": 5.73}, {"text": "okay so there it is in Haskell and I", "start": 621.88, "duration": 6.18}, {"text": "think there's one other thing that", "start": 626.44, "duration": 4.71}, {"text": "really threw people which is like I said", "start": 628.06, "duration": 6.06}, {"text": "it in an italic font so it looks all", "start": 631.15, "duration": 5.85}, {"text": "pretty like mathematics and everybody", "start": 634.12, "duration": 6.72}, {"text": "said Oh mathematics I am not worthy but", "start": 637.0, "duration": 5.97}, {"text": "don't be afraid of mathematics right", "start": 640.84, "duration": 4.53}, {"text": "mathematics is warm and fuzzy and cuddly", "start": 642.97, "duration": 6.09}, {"text": "just like lambdas right are both not", "start": 645.37, "duration": 6.66}, {"text": "many many years ago said if you have a", "start": 649.06, "duration": 4.74}, {"text": "problem they're susceptible to", "start": 652.03, "duration": 5.67}, {"text": "mathematics and you don't use it it is", "start": 653.8, "duration": 5.85}, {"text": "as if you were in the dark and you", "start": 657.7, "duration": 7.26}, {"text": "failed to light a candle mathematics is", "start": 659.65, "duration": 7.8}, {"text": "your friend don't be afraid of it hey", "start": 664.96, "duration": 4.83}, {"text": "you guys can all cope with JavaScript of", "start": 667.45, "duration": 3.96}, {"text": "course you can do with deal with", "start": 669.79, "duration": 5.64}, {"text": "mathematics okay", "start": 671.41, "duration": 7.2}, {"text": "so here's some Scala and what we're", "start": 675.43, "duration": 6.63}, {"text": "going to do is write out a very simple", "start": 678.61, "duration": 5.82}, {"text": "evaluator for arithmetic as a way of", "start": 682.06, "duration": 4.68}, {"text": "motivating why you might want monads and", "start": 684.43, "duration": 5.79}, {"text": "so we just have terms and the term is", "start": 686.74, "duration": 6.15}, {"text": "built in one of two ways it's either a", "start": 690.22, "duration": 5.64}, {"text": "con for constant which contains an", "start": 692.89, "duration": 6.84}, {"text": "integer or it's a div which contains two", "start": 695.86, "duration": 6.27}, {"text": "other terms so these are going to be", "start": 699.73, "duration": 4.56}, {"text": "parse trees representing arithmetic", "start": 702.13, "duration": 4.08}, {"text": "problems built solely from constants and", "start": 704.29, "duration": 5.43}, {"text": "division so for instance here's a term", "start": 706.21, "duration": 6.87}, {"text": "that represents 1932 divided by 2 and", "start": 709.72, "duration": 6.69}, {"text": "then you divide that by 23 okay and", "start": 713.08, "duration": 5.37}, {"text": "here's another term that represents 1", "start": 716.41, "duration": 6.42}, {"text": "divided by 0 nod if you're happy with", "start": 718.45, "duration": 8.73}, {"text": "that most people are not nodding I'm", "start": 722.83, "duration": 8.85}, {"text": "just going to stop right not if you are", "start": 727.18, "duration": 7.16}, {"text": "happy with that", "start": 731.68, "duration": 2.66}, {"text": "you're not nodding ask a question", "start": 735.45, "duration": 4.38}, {"text": "I'll try a third time nod if you're", "start": 740.55, "duration": 5.49}, {"text": "happy with that", "start": 743.98, "duration": 4.26}, {"text": "you're still not nodding you really", "start": 746.04, "duration": 7.33}, {"text": "better ask your question shouldn't the", "start": 748.24, "duration": 7.019}, {"text": "type system stop you from dividing by", "start": 753.37, "duration": 5.67}, {"text": "zero no so yesterday the Croft I", "start": 755.259, "duration": 7.14}, {"text": "mentioned this theorem of Robin Millers", "start": 759.04, "duration": 7.589}, {"text": "well hike programs don't go wrong but", "start": 762.399, "duration": 6.661}, {"text": "wrong has a very specific definition in", "start": 766.629, "duration": 4.5}, {"text": "the newspaper which you met forgot to", "start": 769.06, "duration": 3.959}, {"text": "mention and the specific definition", "start": 771.129, "duration": 4.621}, {"text": "basically means that something like", "start": 773.019, "duration": 6.081}, {"text": "adding a number to a string that's wrong", "start": 775.75, "duration": 6.569}, {"text": "trying to apply a number rather than", "start": 779.1, "duration": 5.89}, {"text": "apply a function that's wrong but", "start": 782.319, "duration": 4.741}, {"text": "dividing one by zero that's not wrong", "start": 784.99, "duration": 5.339}, {"text": "that's bottom so we will catch certain", "start": 787.06, "duration": 5.85}, {"text": "errors but not others so no the type", "start": 790.329, "duration": 4.021}, {"text": "system doesn't prevent you from doing", "start": 792.91, "duration": 3.84}, {"text": "every stupid thing just some stupid", "start": 794.35, "duration": 4.94}, {"text": "things excellent question thank you", "start": 796.75, "duration": 6.689}, {"text": "third time know if you're happy with", "start": 799.29, "duration": 8.409}, {"text": "that all right that's enough naught so I", "start": 803.439, "duration": 6.77}, {"text": "can move on", "start": 807.699, "duration": 2.51}, {"text": "so now we'll write a little evaluator", "start": 810.629, "duration": 5.531}, {"text": "writing it in Scala I'm not that useful", "start": 812.86, "duration": 5.31}, {"text": "Scala so you guys can correct me if I", "start": 816.16, "duration": 4.229}, {"text": "get anything wrong right so eat an", "start": 818.17, "duration": 4.83}, {"text": "evaluator takes a term and it returns an", "start": 820.389, "duration": 4.351}, {"text": "integer and we're going to match on that", "start": 823.0, "duration": 3.54}, {"text": "term and there are two possibilities", "start": 824.74, "duration": 4.17}, {"text": "right it's either a constant or division", "start": 826.54, "duration": 4.62}, {"text": "if it's a constant just return that", "start": 828.91, "duration": 4.619}, {"text": "constant if it's a division evaluate", "start": 831.16, "duration": 4.38}, {"text": "both of the sub terms and then divide", "start": 833.529, "duration": 8.16}, {"text": "the result okay pretty clear okay and", "start": 835.54, "duration": 8.159}, {"text": "then of course if we set a to the result", "start": 841.689, "duration": 4.32}, {"text": "evaluating answer that's a it always is", "start": 843.699, "duration": 4.74}, {"text": "42 you did all that bill did that", "start": 846.009, "duration": 6.0}, {"text": "division right why did I pick the 1932", "start": 848.439, "duration": 5.19}, {"text": "so starting point by the way that's the", "start": 852.009, "duration": 2.971}, {"text": "year in which lambda calculus was", "start": 853.629, "duration": 1.95}, {"text": "invented", "start": 854.98, "duration": 2.609}, {"text": "how many programming languages do you", "start": 855.579, "duration": 3.961}, {"text": "know that were invented before there", "start": 857.589, "duration": 5.761}, {"text": "were any computers lambda calculus is", "start": 859.54, "duration": 6.51}, {"text": "cool okay and then of course if we try", "start": 863.35, "duration": 5.31}, {"text": "to divide by zero then it's the computer", "start": 866.05, "duration": 5.009}, {"text": "explodes right it gives us a divided by", "start": 868.66, "duration": 3.28}, {"text": "zero error", "start": 871.059, "duration": 2.861}, {"text": "we are going to do something about that", "start": 871.94, "duration": 6.44}, {"text": "divide by zero error by the way more RAM", "start": 873.92, "duration": 7.85}, {"text": "that won't help", "start": 878.38, "duration": 3.39}, {"text": "so what are we going to do right what we", "start": 883.749, "duration": 5.32}, {"text": "want if we're trying to divide by zero", "start": 887.299, "duration": 4.08}, {"text": "we want to raise an exception so in the", "start": 889.069, "duration": 4.05}, {"text": "language with side-effects that's easy", "start": 891.379, "duration": 4.5}, {"text": "in a functional language it's also very", "start": 893.119, "duration": 5.52}, {"text": "easy all you need to do is rewrite the", "start": 895.879, "duration": 5.76}, {"text": "entire program so let's see how we would", "start": 898.639, "duration": 8.16}, {"text": "rewrite the entire program so my", "start": 901.639, "duration": 6.18}, {"text": "exception is going to be an error", "start": 906.799, "duration": 2.94}, {"text": "message let's call make let's make those", "start": 907.819, "duration": 3.87}, {"text": "strings and I'm going to find a type", "start": 909.739, "duration": 5.371}, {"text": "called M of a so it's a parameterised", "start": 911.689, "duration": 5.851}, {"text": "type the type is called m and takes a", "start": 915.11, "duration": 5.159}, {"text": "type parameter which is an a what M of a", "start": 917.54, "duration": 5.19}, {"text": "means is a computation that returns a", "start": 920.269, "duration": 8.04}, {"text": "value of type a so in our case so and", "start": 922.73, "duration": 6.839}, {"text": "what is M of a there are two", "start": 928.309, "duration": 1.981}, {"text": "possibilities", "start": 929.569, "duration": 6.0}, {"text": "it's either a raise of an exception so", "start": 930.29, "duration": 10.769}, {"text": "string or its return of an A so right if", "start": 935.569, "duration": 7.71}, {"text": "we return a value of type a we just", "start": 941.059, "duration": 4.47}, {"text": "return it and otherwise we're going to", "start": 943.279, "duration": 3.87}, {"text": "raise an exception so computation does", "start": 945.529, "duration": 4.321}, {"text": "one of two things it raises an exception", "start": 947.149, "duration": 4.711}, {"text": "that is it returns the string as an", "start": 949.85, "duration": 3.81}, {"text": "error message or it returns a value of", "start": 951.86, "duration": 4.169}, {"text": "type a so that's what M of a means in", "start": 953.66, "duration": 6.329}, {"text": "this case see it's easy you just rewrite", "start": 956.029, "duration": 7.05}, {"text": "the whole evaluator so what do we do", "start": 959.989, "duration": 5.491}, {"text": "here um I'll just point at the string", "start": 963.079, "duration": 4.38}, {"text": "rather than turning round can people see", "start": 965.48, "duration": 5.25}, {"text": "that little hand yep okay so we've got s", "start": 967.459, "duration": 5.91}, {"text": "which is a term and we match it right in", "start": 970.73, "duration": 5.269}, {"text": "the two possibility if use a con or div", "start": 973.369, "duration": 5.19}, {"text": "so if it's con of course we just return", "start": 975.999, "duration": 4.541}, {"text": "a so notice now we have to write return", "start": 978.559, "duration": 5.07}, {"text": "around a and notice that the good thing", "start": 980.54, "duration": 5.519}, {"text": "about a type system is that you just", "start": 983.629, "duration": 4.92}, {"text": "said a and you forgot the return the", "start": 986.059, "duration": 4.02}, {"text": "type system would say did you really", "start": 988.549, "duration": 4.561}, {"text": "mean that I don't think so and you'd put", "start": 990.079, "duration": 5.01}, {"text": "in the return to give it the right type", "start": 993.11, "duration": 5.339}, {"text": "which is in this case M event this works", "start": 995.089, "duration": 6.33}, {"text": "right because a is an int so otherwise", "start": 998.449, "duration": 5.43}, {"text": "it's a div of T nu and we're going to", "start": 1001.419, "duration": 5.371}, {"text": "we'll evaluate T of course T is going to", "start": 1003.879, "duration": 4.65}, {"text": "do one of two things it's either going", "start": 1006.79, "duration": 3.779}, {"text": "to give an error message if it does that", "start": 1008.529, "duration": 4.321}, {"text": "will just return that same error message", "start": 1010.569, "duration": 4.49}, {"text": "or", "start": 1012.85, "duration": 2.209}, {"text": "it's going to return some value let's", "start": 1015.1, "duration": 3.42}, {"text": "call it a and then the schools can", "start": 1016.39, "duration": 4.02}, {"text": "evaluate you and it'll do the same thing", "start": 1018.52, "duration": 3.81}, {"text": "if it gives an error message we'll", "start": 1020.41, "duration": 6.36}, {"text": "return it so I will raise it and if it", "start": 1022.33, "duration": 6.57}, {"text": "gives the value B well we'll check and", "start": 1026.77, "duration": 4.41}, {"text": "if B is 0 will give an error message", "start": 1028.9, "duration": 5.01}, {"text": "divided by 0 and otherwise we'll return", "start": 1031.18, "duration": 6.27}, {"text": "a over B so you said why doesn't the", "start": 1033.91, "duration": 5.34}, {"text": "type system get rid of you know tell me", "start": 1037.45, "duration": 3.57}, {"text": "that I'm dividing by 0 so it won't do", "start": 1039.25, "duration": 3.66}, {"text": "that but if you want to say well the", "start": 1041.02, "duration": 5.88}, {"text": "answer is either a value of type A or an", "start": 1042.91, "duration": 5.76}, {"text": "error message it will help you get that", "start": 1046.9, "duration": 6.09}, {"text": "right okay so all we had to do was", "start": 1048.67, "duration": 5.73}, {"text": "rewrite the program in this route", "start": 1052.99, "duration": 3.9}, {"text": "straight forward but revoltingly tedious", "start": 1054.4, "duration": 6.99}, {"text": "way let's try another possibility", "start": 1056.89, "duration": 6.75}, {"text": "oh no let's try it first let's just make", "start": 1061.39, "duration": 6.0}, {"text": "sure it works so let em be eval of", "start": 1063.64, "duration": 8.15}, {"text": "answer and n is going to be return of 42", "start": 1067.39, "duration": 7.56}, {"text": "but now if we do the dare err we get", "start": 1071.79, "duration": 7.96}, {"text": "raised of divided by 0 okay any", "start": 1074.95, "duration": 8.43}, {"text": "questions yet I had a question I've saw", "start": 1079.75, "duration": 5.7}, {"text": "this when I was working on it with Jed", "start": 1083.38, "duration": 4.32}, {"text": "and Toby we're very very helpful and", "start": 1085.45, "duration": 3.42}, {"text": "there will be a special thanks to them", "start": 1087.7, "duration": 3.66}, {"text": "at the end but I said why aren't there", "start": 1088.87, "duration": 3.93}, {"text": "quotation marks around four divided by", "start": 1091.36, "duration": 2.61}, {"text": "zero and they said well that's what", "start": 1092.8, "duration": 5.03}, {"text": "Scala does okay that's what scholar does", "start": 1093.97, "duration": 3.86}, {"text": "so let's look at a different thing to do", "start": 1099.81, "duration": 5.26}, {"text": "we want to count the number of division", "start": 1102.46, "duration": 5.22}, {"text": "operations so that's really easy if you", "start": 1105.07, "duration": 5.67}, {"text": "have global state you can just increment", "start": 1107.68, "duration": 4.53}, {"text": "the global state every time you do a", "start": 1110.74, "duration": 5.13}, {"text": "division operation but what if you don't", "start": 1112.21, "duration": 6.15}, {"text": "have state well that's really easy too", "start": 1115.87, "duration": 4.65}, {"text": "all we need to do is rewrite the entire", "start": 1118.36, "duration": 4.67}, {"text": "program so how are we going to do that", "start": 1120.52, "duration": 5.55}, {"text": "well now let's let's our state be an", "start": 1123.03, "duration": 4.36}, {"text": "integer the count of the number of", "start": 1126.07, "duration": 3.57}, {"text": "division operations and something of", "start": 1127.39, "duration": 6.08}, {"text": "type M of a is the computation that", "start": 1129.64, "duration": 7.35}, {"text": "updates the state and returns a value of", "start": 1133.47, "duration": 5.83}, {"text": "type a so it takes the current state as", "start": 1136.99, "duration": 5.19}, {"text": "input and it returns a pair of a the", "start": 1139.3, "duration": 6.47}, {"text": "answer whose type is a and the new state", "start": 1142.18, "duration": 6.79}, {"text": "so function from current state to", "start": 1145.77, "duration": 6.86}, {"text": "answer a new state so now eval is going", "start": 1148.97, "duration": 5.699}, {"text": "to take a term and return an M of int", "start": 1152.63, "duration": 6.84}, {"text": "and we'll match s and if it's a constant", "start": 1154.669, "duration": 7.26}, {"text": "then we don't change the state at all so", "start": 1159.47, "duration": 4.62}, {"text": "we take as input the state X and we", "start": 1161.929, "duration": 6.811}, {"text": "return an ax pair okay", "start": 1164.09, "duration": 7.62}, {"text": "take the input state return the answer", "start": 1168.74, "duration": 5.64}, {"text": "which is in this case a and return the", "start": 1171.71, "duration": 4.8}, {"text": "same state unchanged state doesn't", "start": 1174.38, "duration": 6.06}, {"text": "change no assignment okay so this arrow", "start": 1176.51, "duration": 6.18}, {"text": "here this is Scala's wave writing lambda", "start": 1180.44, "duration": 4.92}, {"text": "in lambda calculus you'd write lambda X", "start": 1182.69, "duration": 7.619}, {"text": "of type int returns and a X pair okay", "start": 1185.36, "duration": 7.049}, {"text": "not if you're happy you know what will", "start": 1190.309, "duration": 5.011}, {"text": "happen if you don't nod not if you're", "start": 1192.409, "duration": 8.581}, {"text": "happy you're not nodding ah you're", "start": 1195.32, "duration": 9.989}, {"text": "nodding imperceptibly okay we'll move on", "start": 1200.99, "duration": 6.569}, {"text": "any questions I'm not getting enough", "start": 1205.309, "duration": 4.921}, {"text": "questions here any questions okay", "start": 1207.559, "duration": 5.73}, {"text": "this is boring right it's easy to do but", "start": 1210.23, "duration": 4.59}, {"text": "it's boring it's tedious please", "start": 1213.289, "duration": 3.75}, {"text": "straightforward so if now if we're", "start": 1214.82, "duration": 4.56}, {"text": "dividing T by you we take the current", "start": 1217.039, "duration": 5.551}, {"text": "state X and eval T takes the current", "start": 1219.38, "duration": 5.64}, {"text": "state X as an additional target the", "start": 1222.59, "duration": 4.89}, {"text": "input state what will we get back and a", "start": 1225.02, "duration": 5.61}, {"text": "white air a is the answer y is the new", "start": 1227.48, "duration": 6.24}, {"text": "tape takes the new state pass that into", "start": 1230.63, "duration": 7.2}, {"text": "eval of you get out the answer B and a", "start": 1233.72, "duration": 6.54}, {"text": "final state Zed and then our final state", "start": 1237.83, "duration": 4.44}, {"text": "for the whole thing is a divided by B", "start": 1240.26, "duration": 5.909}, {"text": "that's the answer and red plus one so", "start": 1242.27, "duration": 5.7}, {"text": "now we're incrementing the current state", "start": 1246.169, "duration": 6.421}, {"text": "and then if we execute eval of answer we", "start": 1247.97, "duration": 6.209}, {"text": "have to give it the initial state zero", "start": 1252.59, "duration": 4.56}, {"text": "and it returns the final state to as", "start": 1254.179, "duration": 6.661}, {"text": "well as the answer 42 okay", "start": 1257.15, "duration": 6.84}, {"text": "not clear enough to everybody so it's", "start": 1260.84, "duration": 8.18}, {"text": "easy but very very tedious", "start": 1263.99, "duration": 5.03}, {"text": "three I want to trace the execution of", "start": 1271.83, "duration": 7.06}, {"text": "my program so again normally I would", "start": 1274.72, "duration": 5.97}, {"text": "just write some output to the terminal", "start": 1278.89, "duration": 3.899}, {"text": "but I don't have writing output as a", "start": 1280.69, "duration": 3.989}, {"text": "side-effect so what shall I do", "start": 1282.789, "duration": 4.591}, {"text": "let's I think it's pretty easy let's", "start": 1284.679, "duration": 8.691}, {"text": "just rewrite the whole program so now a", "start": 1287.38, "duration": 8.7}, {"text": "computation that returns an A is going", "start": 1293.37, "duration": 4.779}, {"text": "to return some output paired with an A", "start": 1296.08, "duration": 6.69}, {"text": "and output will just be a string and so", "start": 1298.149, "duration": 6.51}, {"text": "to evaluate something it's going to", "start": 1302.77, "duration": 4.769}, {"text": "return an output integer pair match on s", "start": 1304.659, "duration": 5.64}, {"text": "again if it's a constant then return", "start": 1307.539, "duration": 4.951}, {"text": "some output saying I just evaluated a", "start": 1310.299, "duration": 4.11}, {"text": "constant and we can do that by saying", "start": 1312.49, "duration": 5.76}, {"text": "the line takes the term s and on the", "start": 1314.409, "duration": 7.171}, {"text": "answer a and it says so line takes a", "start": 1318.25, "duration": 6.69}, {"text": "term and an integer and replaces this", "start": 1321.58, "duration": 8.339}, {"text": "term equal sign the answer new line so", "start": 1324.94, "duration": 7.68}, {"text": "we place print that line or return that", "start": 1329.919, "duration": 5.191}, {"text": "line as output and return the answer a", "start": 1332.62, "duration": 5.64}, {"text": "and if we're doing a division so X's", "start": 1335.11, "duration": 6.15}, {"text": "will evaluate T X is the output a is the", "start": 1338.26, "duration": 6.899}, {"text": "answer will evaluate you Y is the output", "start": 1341.26, "duration": 6.09}, {"text": "B is the answer and then for the final", "start": 1345.159, "duration": 3.211}, {"text": "thing we'll place", "start": 1347.35, "duration": 3.39}, {"text": "print all the output from T all the", "start": 1348.37, "duration": 6.299}, {"text": "output from you a line saying astra", "start": 1350.74, "duration": 5.7}, {"text": "number S will be dipped to you I divided", "start": 1354.669, "duration": 4.23}, {"text": "T by you and the answer was a divided by", "start": 1356.44, "duration": 5.219}, {"text": "B and I'll return the answer a divided", "start": 1358.899, "duration": 7.921}, {"text": "by B okay clear enough right so at this", "start": 1361.659, "duration": 7.591}, {"text": "point hey you should all be nodding your", "start": 1366.82, "duration": 5.79}, {"text": "heads right and B you'd all be bored", "start": 1369.25, "duration": 5.309}, {"text": "silly and see somebody's actually asking", "start": 1372.61, "duration": 5.09}, {"text": "a question thank you yes", "start": 1374.559, "duration": 8.551}, {"text": "sorry I can't hear you why are we", "start": 1377.7, "duration": 8.17}, {"text": "calculating state and output so in this", "start": 1383.11, "duration": 4.799}, {"text": "case we were doing some state because we", "start": 1385.87, "duration": 3.36}, {"text": "wanted to count the number of division", "start": 1387.909, "duration": 3.51}, {"text": "operations you might have variant", "start": 1389.23, "duration": 3.689}, {"text": "recognize take they're better ways of", "start": 1391.419, "duration": 3.421}, {"text": "doing that than counting right I could", "start": 1392.919, "duration": 4.171}, {"text": "just have every operation return the", "start": 1394.84, "duration": 4.02}, {"text": "number of operations it did and then add", "start": 1397.09, "duration": 3.329}, {"text": "them all together that would be better", "start": 1398.86, "duration": 3.24}, {"text": "but I wanted something that involves", "start": 1400.419, "duration": 4.381}, {"text": "state so I did that because you", "start": 1402.1, "duration": 4.35}, {"text": "no of many computations where you do", "start": 1404.8, "duration": 3.42}, {"text": "need to pass state around a database a", "start": 1406.45, "duration": 4.2}, {"text": "and similarly sometimes you need to", "start": 1408.22, "duration": 3.66}, {"text": "trace things so that's why I'm doing", "start": 1410.65, "duration": 2.91}, {"text": "output here but again you'll think of", "start": 1411.88, "duration": 3.39}, {"text": "many things where you need to do output", "start": 1413.56, "duration": 3.21}, {"text": "or many things where you need to raise", "start": 1415.27, "duration": 3.75}, {"text": "exceptions so I've tried to take", "start": 1416.77, "duration": 4.14}, {"text": "examples so they're simple enough that", "start": 1419.02, "duration": 4.05}, {"text": "can cover them in a one-hour talk but", "start": 1420.91, "duration": 3.72}, {"text": "you will all be able to think of many", "start": 1423.07, "duration": 3.36}, {"text": "other things like this that you want to", "start": 1424.63, "duration": 5.25}, {"text": "do and you're nodding excellent thank", "start": 1426.43, "duration": 6.9}, {"text": "you okay but the point is by now you", "start": 1429.88, "duration": 5.73}, {"text": "should be bored okay yes I can do all of", "start": 1433.33, "duration": 4.35}, {"text": "these things yes the programs are", "start": 1435.61, "duration": 3.66}, {"text": "straightforward but they are very", "start": 1437.68, "duration": 4.5}, {"text": "tedious to write all right and let's", "start": 1439.27, "duration": 5.13}, {"text": "yeah so if we do Bell is out of answer", "start": 1442.18, "duration": 3.45}, {"text": "right we get the output well first I", "start": 1444.4, "duration": 4.77}, {"text": "evaluated in 1932 to 1932 then a value", "start": 1445.63, "duration": 7.28}, {"text": "80222 9 divided in 1932 by - that was", "start": 1449.17, "duration": 7.5}, {"text": "966 and I evaluate 23 to 23 and then the", "start": 1452.91, "duration": 6.4}, {"text": "whole expression evaluates to 42 and 42", "start": 1456.67, "duration": 5.88}, {"text": "is the answer okay so straightforward", "start": 1459.31, "duration": 7.14}, {"text": "but boring and tedious so here's what", "start": 1462.55, "duration": 5.37}, {"text": "we're going to do about the boring", "start": 1466.45, "duration": 2.85}, {"text": "tedious part right you'll recognize that", "start": 1467.92, "duration": 3.0}, {"text": "that slides they have this weird", "start": 1469.3, "duration": 3.09}, {"text": "background that's from the actual", "start": 1470.92, "duration": 7.68}, {"text": "original talk so what we're going to do", "start": 1472.39, "duration": 10.32}, {"text": "is define a monad back to the dictionary", "start": 1478.6, "duration": 8.97}, {"text": "known add now 1 be in the metaphysics of", "start": 1482.71, "duration": 7.98}, {"text": "line that's a simple indestructible", "start": 1487.57, "duration": 6.48}, {"text": "non-spatial element regarded as the unit", "start": 1490.69, "duration": 7.71}, {"text": "of which reality consists ok so you're", "start": 1494.05, "duration": 7.13}, {"text": "ready to see what that is", "start": 1498.4, "duration": 6.45}, {"text": "so it's just three things and remember", "start": 1501.18, "duration": 5.53}, {"text": "category theorist has this for", "start": 1504.85, "duration": 4.5}, {"text": "completely different reasons category", "start": 1506.71, "duration": 4.17}, {"text": "theorists were interested in problems in", "start": 1509.35, "duration": 4.53}, {"text": "algebraic topology of all things but for", "start": 1510.88, "duration": 4.89}, {"text": "that they needed this kind of structure", "start": 1513.88, "duration": 5.31}, {"text": "so it has three things number one for", "start": 1515.77, "duration": 6.99}, {"text": "each type a of values a type M of a to", "start": 1519.19, "duration": 5.28}, {"text": "represent computation so you probably", "start": 1522.76, "duration": 3.93}, {"text": "figured out what the Big M stands for", "start": 1524.47, "duration": 6.03}, {"text": "and in general what we're going to do", "start": 1526.69, "duration": 6.03}, {"text": "take a function from A to B and that's", "start": 1530.5, "duration": 4.26}, {"text": "going to become a function from A to M", "start": 1532.72, "duration": 6.29}, {"text": "of B that's the key idea", "start": 1534.76, "duration": 6.72}, {"text": "right and you've seen three examples of", "start": 1539.01, "duration": 4.63}, {"text": "that where we took eval which take", "start": 1541.48, "duration": 4.05}, {"text": "determine returns an integer and we've", "start": 1543.64, "duration": 3.81}, {"text": "turned it into eval which takes a term", "start": 1545.53, "duration": 5.46}, {"text": "and returns an M of integer and n is our", "start": 1547.45, "duration": 6.0}, {"text": "computation with computational effects", "start": 1550.99, "duration": 5.97}, {"text": "such as raising exceptions changing", "start": 1553.45, "duration": 7.02}, {"text": "state or printing output okay and then", "start": 1556.96, "duration": 6.81}, {"text": "we're going to need two things to go", "start": 1560.47, "duration": 5.79}, {"text": "with this first a way to turn values", "start": 1563.77, "duration": 4.74}, {"text": "into computations we're going to call", "start": 1566.26, "duration": 5.94}, {"text": "that pure so pure takes a value a of", "start": 1568.51, "duration": 6.66}, {"text": "type a and returns a value of type M of", "start": 1572.2, "duration": 4.83}, {"text": "a so this is the computation that", "start": 1575.17, "duration": 5.19}, {"text": "returns the answer little a of type big", "start": 1577.03, "duration": 6.75}, {"text": "a without doing anything else so it", "start": 1580.36, "duration": 6.0}, {"text": "leaves the state unchanged it raises no", "start": 1583.78, "duration": 6.08}, {"text": "exception or it prints no output and", "start": 1586.36, "duration": 5.81}, {"text": "then we need a way to combine", "start": 1589.86, "duration": 5.56}, {"text": "computations this is called bind and", "start": 1592.17, "duration": 6.1}, {"text": "this is the weird one so barn takes a", "start": 1595.42, "duration": 5.31}, {"text": "computation M that returns a value of", "start": 1598.27, "duration": 4.98}, {"text": "type a and now we want to do something", "start": 1600.73, "duration": 5.94}, {"text": "with that value of type a okay but we've", "start": 1603.25, "duration": 6.81}, {"text": "got something a type M of a and what we", "start": 1606.67, "duration": 4.38}, {"text": "want is something that does something", "start": 1610.06, "duration": 3.03}, {"text": "with V a so that's something that does", "start": 1611.05, "duration": 6.69}, {"text": "something with VA is called K which in", "start": 1613.09, "duration": 6.87}, {"text": "fact think of continuation that's why we", "start": 1617.74, "duration": 5.31}, {"text": "use K and the rest of the computation", "start": 1619.96, "duration": 6.69}, {"text": "the continuation takes the value a so", "start": 1623.05, "duration": 6.12}, {"text": "this is an a not an M of a and it", "start": 1626.65, "duration": 4.65}, {"text": "returns the computation of type B then", "start": 1629.17, "duration": 3.54}, {"text": "we put those together and the whole", "start": 1631.3, "duration": 5.58}, {"text": "thing is a computation of type B so in", "start": 1632.71, "duration": 6.42}, {"text": "language with side-effects this is just", "start": 1636.88, "duration": 7.2}, {"text": "a let expression evaluate m and then if", "start": 1639.13, "duration": 8.34}, {"text": "we wrote K is lambda X and it means bind", "start": 1644.08, "duration": 6.57}, {"text": "X to the value returned by M and then do", "start": 1647.47, "duration": 7.46}, {"text": "n so this would be let X equal m in N if", "start": 1650.65, "duration": 7.35}, {"text": "K was lambda X and then some expression", "start": 1654.93, "duration": 5.11}, {"text": "man so we'll see lots of examples", "start": 1658.0, "duration": 4.52}, {"text": "question", "start": 1660.04, "duration": 2.48}, {"text": "do I have a typo oh yeah there is a typo", "start": 1666.41, "duration": 12.04}, {"text": "thank you hey guys right so Toby we're", "start": 1673.38, "duration": 6.69}, {"text": "helping we do this and we must have it's", "start": 1678.45, "duration": 3.57}, {"text": "all running you can actually download it", "start": 1680.07, "duration": 3.6}, {"text": "from the web so we must have made an", "start": 1682.02, "duration": 3.18}, {"text": "error in typesetting it so this is", "start": 1683.67, "duration": 4.11}, {"text": "actually find of a comma B because both", "start": 1685.2, "duration": 5.58}, {"text": "a and B are types used by this thing and", "start": 1687.78, "duration": 5.91}, {"text": "the type inference system of Scala will", "start": 1690.78, "duration": 5.22}, {"text": "just infer a and B for you so we won't", "start": 1693.69, "duration": 7.02}, {"text": "need to write those all the time okay", "start": 1696.0, "duration": 7.14}, {"text": "and then these satisfy some laws this is", "start": 1700.71, "duration": 4.02}, {"text": "the only mathematics you'll see in the", "start": 1703.14, "duration": 4.38}, {"text": "talk and I'm not even going to go", "start": 1704.73, "duration": 4.26}, {"text": "through the details of how these work", "start": 1707.52, "duration": 4.05}, {"text": "but you're guaranteed that these if you", "start": 1708.99, "duration": 4.5}, {"text": "ever write that expression it's the same", "start": 1711.57, "duration": 3.57}, {"text": "as that one if you ever write that", "start": 1713.49, "duration": 3.57}, {"text": "expression it's the same as that one if", "start": 1715.14, "duration": 3.87}, {"text": "you ever write that expression it's the", "start": 1717.06, "duration": 4.5}, {"text": "same as that one and these happen to", "start": 1719.01, "duration": 5.79}, {"text": "look like the left unit right unit and", "start": 1721.56, "duration": 5.94}, {"text": "associative laws of a mono IDE okay", "start": 1724.8, "duration": 5.19}, {"text": "there's a scary word mono a it's the", "start": 1727.5, "duration": 4.95}, {"text": "name in mathematics for an operator and", "start": 1729.99, "duration": 5.94}, {"text": "a constant such that the constant is the", "start": 1732.45, "duration": 7.14}, {"text": "unit of the operator and the operator is", "start": 1735.93, "duration": 8.97}, {"text": "associative examples 0 and plus 1 and", "start": 1739.59, "duration": 13.89}, {"text": "times true and and false and or empty", "start": 1744.9, "duration": 10.92}, {"text": "string and string concatenation those", "start": 1753.48, "duration": 4.92}, {"text": "are all examples of mono 'its so if you", "start": 1755.82, "duration": 4.29}, {"text": "want to know where the name monad comes", "start": 1758.4, "duration": 5.1}, {"text": "from it's just a pun on mono I'd write", "start": 1760.11, "duration": 5.58}, {"text": "and category theorist or pretentious so", "start": 1763.5, "duration": 3.96}, {"text": "they like to adopt names from philosophy", "start": 1765.69, "duration": 4.5}, {"text": "which is why they use likenesses term", "start": 1767.46, "duration": 5.67}, {"text": "also used by other philosophers of monad", "start": 1770.19, "duration": 6.36}, {"text": "ok so now it's demystified where it", "start": 1773.13, "duration": 5.72}, {"text": "comes from", "start": 1776.55, "duration": 2.3}, {"text": "ok so now here's the payoff what happens", "start": 1779.6, "duration": 7.12}, {"text": "to our evaluator well we need more of", "start": 1783.78, "duration": 4.37}, {"text": "the definition of blown-out of course", "start": 1786.72, "duration": 5.49}, {"text": "monad noun 1 see in the pantheistic", "start": 1788.15, "duration": 6.96}, {"text": "philosophy of Giordano Bruno a", "start": 1792.21, "duration": 4.56}, {"text": "fundamental benefits", "start": 1795.11, "duration": 5.01}, {"text": "unit they did spatially extended and", "start": 1796.77, "duration": 9.24}, {"text": "psychically aware alright so what can we", "start": 1800.12, "duration": 10.3}, {"text": "do with our psychically aware monads so", "start": 1806.01, "duration": 6.12}, {"text": "will now go through and redo our", "start": 1810.42, "duration": 4.65}, {"text": "examples and see what had been tedious", "start": 1812.13, "duration": 6.0}, {"text": "and annoying becomes straightforward by", "start": 1815.07, "duration": 8.79}, {"text": "using a monad so first let's just look", "start": 1818.13, "duration": 7.62}, {"text": "at the simplest monads the one that does", "start": 1823.86, "duration": 6.14}, {"text": "nothing whatsoever the identity monad so", "start": 1825.75, "duration": 7.08}, {"text": "we'll just define an of a to be a a", "start": 1830.0, "duration": 4.929}, {"text": "computation that returns an a is just", "start": 1832.83, "duration": 4.26}, {"text": "the value of type a and nothing else", "start": 1834.929, "duration": 4.831}, {"text": "so what's pure do it does nothing it", "start": 1837.09, "duration": 4.98}, {"text": "just returns the a and what does bind do", "start": 1839.76, "duration": 4.56}, {"text": "well we're taking the same feeding it", "start": 1842.07, "duration": 3.75}, {"text": "indicate how will we do that", "start": 1844.32, "duration": 7.59}, {"text": "just apply k to a and then we can", "start": 1845.82, "duration": 9.87}, {"text": "rewrite our evaluator in this style so", "start": 1851.91, "duration": 5.91}, {"text": "again look at the term if it's a", "start": 1855.69, "duration": 4.619}, {"text": "constant now we need to return an M of a", "start": 1857.82, "duration": 7.44}, {"text": "so return pure of a right to bit as long", "start": 1860.309, "duration": 6.781}, {"text": "as you have any this works in any monad", "start": 1865.26, "duration": 3.9}, {"text": "whatsoever this works in the identity", "start": 1867.09, "duration": 3.93}, {"text": "monad and all the other monads that", "start": 1869.16, "duration": 3.87}, {"text": "we'll see so the point is we've now", "start": 1871.02, "duration": 4.409}, {"text": "generalize so that this piece of code", "start": 1873.03, "duration": 4.67}, {"text": "works for any kind of computation", "start": 1875.429, "duration": 5.341}, {"text": "whatsoever as long as it has a pure", "start": 1877.7, "duration": 5.59}, {"text": "operation and a bind operation and by", "start": 1880.77, "duration": 4.83}, {"text": "the way you can test those three laws to", "start": 1883.29, "duration": 4.889}, {"text": "see to have a sensible pure and bind", "start": 1885.6, "duration": 6.63}, {"text": "operation so if it's a constant do", "start": 1888.179, "duration": 9.571}, {"text": "nothing just return a so pure of a if", "start": 1892.23, "duration": 9.27}, {"text": "it's a division evaluate T this will be", "start": 1897.75, "duration": 7.95}, {"text": "an M of int and we want the integer a so", "start": 1901.5, "duration": 8.76}, {"text": "bind a to the answer from eval of T and", "start": 1905.7, "duration": 6.99}, {"text": "then evaluate you and bind B to the", "start": 1910.26, "duration": 5.52}, {"text": "answer of eval of you and then just", "start": 1912.69, "duration": 5.16}, {"text": "divide a by B and return to this pure", "start": 1915.78, "duration": 4.86}, {"text": "here is where types really get to be", "start": 1917.85, "duration": 5.94}, {"text": "your friend say that I omitted one of", "start": 1920.64, "duration": 6.15}, {"text": "those binds by mistake and just said let", "start": 1923.79, "duration": 6.45}, {"text": "a be the answer of this or or I admit", "start": 1926.79, "duration": 3.99}, {"text": "both", "start": 1930.24, "duration": 2.49}, {"text": "or I omitted the pure by mistake the", "start": 1930.78, "duration": 4.47}, {"text": "type checker will tell you this is", "start": 1932.73, "duration": 5.43}, {"text": "pretty much the only program that has", "start": 1935.25, "duration": 6.15}, {"text": "the right type right as long as we're", "start": 1938.16, "duration": 5.55}, {"text": "actually evaluating P evaluating you and", "start": 1941.4, "duration": 4.92}, {"text": "dividing the answers so the types get", "start": 1943.71, "duration": 4.35}, {"text": "all the mess of passing the monads", "start": 1946.32, "duration": 5.06}, {"text": "around they force you to get that right", "start": 1948.06, "duration": 5.55}, {"text": "right you could do something wrong you", "start": 1951.38, "duration": 5.8}, {"text": "can divide B by a instead of a by B but", "start": 1953.61, "duration": 6.21}, {"text": "the types force you to get the structure", "start": 1957.18, "duration": 5.37}, {"text": "of passing things around correct that is", "start": 1959.82, "duration": 8.64}, {"text": "where the types really help so now how", "start": 1962.55, "duration": 8.43}, {"text": "would we do exceptions so as before", "start": 1968.46, "duration": 5.79}, {"text": "we'll define M of a to be raised or", "start": 1970.98, "duration": 7.4}, {"text": "return and then pure is just return and", "start": 1974.25, "duration": 8.25}, {"text": "bind says well if we've gotten an ammo", "start": 1978.38, "duration": 7.39}, {"text": "type big M of a so we'll match it if", "start": 1982.5, "duration": 5.73}, {"text": "it's raised of e than just raising again", "start": 1985.77, "duration": 8.88}, {"text": "if it's return of a then we need to pass", "start": 1988.23, "duration": 8.51}, {"text": "this a in to the subsequent computation", "start": 1994.65, "duration": 4.71}, {"text": "which will return an M of B and that'll", "start": 1996.74, "duration": 4.03}, {"text": "be the type returned by the whole thing", "start": 1999.36, "duration": 4.5}, {"text": "so just apply K to a just as in the", "start": 2000.77, "duration": 8.25}, {"text": "identity mount app again this is pretty", "start": 2003.86, "duration": 7.77}, {"text": "much the only thing that has if you've", "start": 2009.02, "duration": 5.28}, {"text": "got that type and you know how M of a is", "start": 2011.63, "duration": 4.98}, {"text": "defined that's the only thing that has", "start": 2014.3, "duration": 5.28}, {"text": "that type Leonard Alderson has actually", "start": 2016.61, "duration": 5.13}, {"text": "written a program that given types gives", "start": 2019.58, "duration": 4.17}, {"text": "terms of that type it will return this", "start": 2021.74, "duration": 4.85}, {"text": "term so the type tells you what to do", "start": 2023.75, "duration": 5.4}, {"text": "and then finally there's one more thing", "start": 2026.59, "duration": 4.18}, {"text": "we need like you can think of this as an", "start": 2029.15, "duration": 5.13}, {"text": "abstract data type now and it's a monad", "start": 2030.77, "duration": 6.18}, {"text": "so it's got pure and vine and two monads", "start": 2034.28, "duration": 4.59}, {"text": "that can raise exceptions so it also has", "start": 2036.95, "duration": 6.06}, {"text": "a raise operator and what raise does is", "start": 2038.87, "duration": 5.64}, {"text": "of course given a string it just", "start": 2043.01, "duration": 3.78}, {"text": "returned so little our arrays just", "start": 2044.51, "duration": 6.03}, {"text": "invokes big are raised and that's all we", "start": 2046.79, "duration": 6.57}, {"text": "need like go back this is exactly the", "start": 2050.54, "duration": 5.16}, {"text": "same evaluator that we had before we", "start": 2053.36, "duration": 5.16}, {"text": "only need to change one bit which is", "start": 2055.7, "duration": 5.04}, {"text": "we've changed the answer before which is", "start": 2058.52, "duration": 4.77}, {"text": "pure of a divided by B but now it's if", "start": 2060.74, "duration": 3.09}, {"text": "the", "start": 2063.29, "duration": 4.11}, {"text": "zero raise / zero otherwise pure of a", "start": 2063.83, "duration": 6.54}, {"text": "divided by B and the rest is exactly the", "start": 2067.4, "duration": 5.19}, {"text": "same as before so now instead of having", "start": 2070.37, "duration": 5.1}, {"text": "to completely rewrite our evaluator we", "start": 2072.59, "duration": 6.65}, {"text": "just add the stuff we want", "start": 2075.47, "duration": 3.77}, {"text": "how about state again M of a is defined", "start": 2080.62, "duration": 7.81}, {"text": "as before it takes the old state and it", "start": 2084.89, "duration": 6.9}, {"text": "returns a value of type a paired with", "start": 2088.43, "duration": 6.45}, {"text": "the new state so pure does no", "start": 2091.79, "duration": 5.13}, {"text": "computation it just returns a value type", "start": 2094.88, "duration": 4.44}, {"text": "a so it takes the state and returns a", "start": 2096.92, "duration": 6.75}, {"text": "paired with the same state and that's", "start": 2099.32, "duration": 5.61}, {"text": "too hard to look at I'm going to do it", "start": 2103.67, "duration": 7.11}, {"text": "here and then bind it's going to return", "start": 2104.93, "duration": 8.25}, {"text": "in MFE so this must be something that", "start": 2110.78, "duration": 4.74}, {"text": "takes the initial state and returns B", "start": 2113.18, "duration": 4.77}, {"text": "and the new state so there's X that's", "start": 2115.52, "duration": 5.67}, {"text": "the initial State evaluate M applied to", "start": 2117.95, "duration": 5.88}, {"text": "X so we passed the old state into M we", "start": 2121.19, "duration": 4.85}, {"text": "get out the answer a and the new state Y", "start": 2123.83, "duration": 7.26}, {"text": "pass up like a to a that's the type M of", "start": 2126.04, "duration": 7.96}, {"text": "B is then expect the current state which", "start": 2131.09, "duration": 5.94}, {"text": "in this case will be Y and we get out", "start": 2134.0, "duration": 5.37}, {"text": "the final answer B paragraph said and", "start": 2137.03, "duration": 4.83}, {"text": "then we return a B's that pair notice I", "start": 2139.37, "duration": 3.81}, {"text": "could have written this more concisely", "start": 2141.86, "duration": 5.1}, {"text": "as just fell a y equals M of B and then", "start": 2143.18, "duration": 7.64}, {"text": "return K of a applied to Y and then", "start": 2146.96, "duration": 6.09}, {"text": "we'll need one more thing in this case", "start": 2150.82, "duration": 5.8}, {"text": "tik tik returns M of unit unit is the", "start": 2153.05, "duration": 5.49}, {"text": "type that has no interesting values in", "start": 2156.62, "duration": 3.51}, {"text": "it so the one uninteresting value of", "start": 2158.54, "duration": 3.96}, {"text": "type unit is written as the empty tuple", "start": 2160.13, "duration": 4.86}, {"text": "open parentheses close parentheses and M", "start": 2162.5, "duration": 6.3}, {"text": "of unit takes the input state returns no", "start": 2164.99, "duration": 5.73}, {"text": "interesting value and increments the", "start": 2168.8, "duration": 4.08}, {"text": "state by 1 so this is what changes the", "start": 2170.72, "duration": 5.88}, {"text": "state tik and in general for state monad", "start": 2172.88, "duration": 5.49}, {"text": "you might have an operation here that", "start": 2176.6, "duration": 3.45}, {"text": "changes the state however you want might", "start": 2178.37, "duration": 3.9}, {"text": "have get and set operations on the state", "start": 2180.05, "duration": 6.06}, {"text": "and then our dilator is just the same as", "start": 2182.27, "duration": 6.42}, {"text": "before we just change one line we put in", "start": 2186.11, "duration": 6.63}, {"text": "a tick before doing the division so now", "start": 2188.69, "duration": 5.52}, {"text": "we will count the number of division", "start": 2192.74, "duration": 3.62}, {"text": "operations", "start": 2194.21, "duration": 4.85}, {"text": "and write this program essentially is", "start": 2196.36, "duration": 4.98}, {"text": "just the one we saw before but we don't", "start": 2199.06, "duration": 4.19}, {"text": "need to rewrite everything tediously", "start": 2201.34, "duration": 4.5}, {"text": "like this is just the one we saw before", "start": 2203.25, "duration": 4.54}, {"text": "after you expand out all the binds and", "start": 2205.84, "duration": 4.05}, {"text": "the peers but you don't need to rewrite", "start": 2207.79, "duration": 5.49}, {"text": "everything tediously and finally for", "start": 2209.89, "duration": 7.14}, {"text": "output so MFA is now the output paired", "start": 2213.28, "duration": 6.57}, {"text": "with a pure obey is going to return an a", "start": 2217.03, "duration": 5.13}, {"text": "and no output so it's no output paired", "start": 2219.85, "duration": 5.48}, {"text": "with a bind", "start": 2222.16, "duration": 7.44}, {"text": "take some and add a decay again and what", "start": 2225.33, "duration": 5.95}, {"text": "are we going to do well M is going to", "start": 2229.6, "duration": 5.25}, {"text": "return output X and answer a we take K", "start": 2231.28, "duration": 6.15}, {"text": "apply to the answer a it will return", "start": 2234.85, "duration": 5.61}, {"text": "output Y and answer B and then we return", "start": 2237.43, "duration": 7.55}, {"text": "the append of x and y and the answer B", "start": 2240.46, "duration": 6.93}, {"text": "then we need one more operation again", "start": 2244.98, "duration": 5.98}, {"text": "output that takes a string and of course", "start": 2247.39, "duration": 5.94}, {"text": "it returns the string paired with a", "start": 2250.96, "duration": 4.62}, {"text": "value that's not of interest so it's an", "start": 2253.33, "duration": 7.08}, {"text": "M of unit any questions is that clear", "start": 2255.58, "duration": 5.07}, {"text": "enough", "start": 2260.41, "duration": 4.49}, {"text": "and again our program is just as before", "start": 2260.65, "duration": 6.42}, {"text": "except now we've got one more operation", "start": 2264.9, "duration": 4.69}, {"text": "we do an output of line si before", "start": 2267.07, "duration": 5.16}, {"text": "returning pure of a for con and we do an", "start": 2269.59, "duration": 4.95}, {"text": "output of line s and a divided by B", "start": 2272.23, "duration": 5.48}, {"text": "before returning pure of a and B and", "start": 2274.54, "duration": 5.82}, {"text": "again this simplifies just to what we", "start": 2277.71, "duration": 10.33}, {"text": "saw before that is it you are now expert", "start": 2280.36, "duration": 14.18}, {"text": "at monads any questions yes", "start": 2288.04, "duration": 6.5}, {"text": "am i implying that monads are exciting", "start": 2299.42, "duration": 6.669}, {"text": "because they give state output and", "start": 2303.18, "duration": 4.549}, {"text": "exceptions to functional languages", "start": 2306.089, "duration": 5.16}, {"text": "absolutely question the answer is sort", "start": 2307.729, "duration": 7.75}, {"text": "of yes they are exciting because they", "start": 2311.249, "duration": 6.48}, {"text": "give you those three things but they", "start": 2315.479, "duration": 4.951}, {"text": "also give you pretty much anything else", "start": 2317.729, "duration": 4.431}, {"text": "you can imagine", "start": 2320.43, "duration": 4.559}, {"text": "so in a language with side effects you", "start": 2322.16, "duration": 4.809}, {"text": "are limited to the side effects built", "start": 2324.989, "duration": 4.891}, {"text": "into the language but you can define a", "start": 2326.969, "duration": 5.55}, {"text": "monad for any of these three effects and", "start": 2329.88, "duration": 6.06}, {"text": "many many many others so you can have", "start": 2332.519, "duration": 5.79}, {"text": "monads to melt Matt to deal with", "start": 2335.94, "duration": 6.559}, {"text": "multiple answers lists of answers", "start": 2338.309, "duration": 7.41}, {"text": "streams of answers you have monads to", "start": 2342.499, "duration": 5.5}, {"text": "deal with concurrency so I'm not going", "start": 2345.719, "duration": 3.661}, {"text": "to go into all the different kinds of", "start": 2347.999, "duration": 3.391}, {"text": "images you can have you have monads to", "start": 2349.38, "duration": 4.649}, {"text": "deal with probability so you label each", "start": 2351.39, "duration": 5.31}, {"text": "answer with how likely it is so there", "start": 2354.029, "duration": 4.44}, {"text": "are all sorts of different things that", "start": 2356.7, "duration": 3.75}, {"text": "fall out of this among which are", "start": 2358.469, "duration": 5.3}, {"text": "included exceptions state and output", "start": 2360.45, "duration": 5.43}, {"text": "suggesting you to do exception state an", "start": 2363.769, "duration": 4.0}, {"text": "output that would be pretty cool but in", "start": 2365.88, "duration": 5.25}, {"text": "fact we can do so much more we can do a", "start": 2367.769, "duration": 5.49}, {"text": "huge variety of things and when I first", "start": 2371.13, "duration": 4.649}, {"text": "bumped in to monads I thought well gosh", "start": 2373.259, "duration": 4.171}, {"text": "it looks like you can do everything with", "start": 2375.779, "duration": 4.74}, {"text": "these why is that eventually we've found", "start": 2377.43, "duration": 4.5}, {"text": "some things that weren't lowness but a", "start": 2380.519, "duration": 3.871}, {"text": "huge variety of things can be done with", "start": 2381.93, "duration": 4.76}, {"text": "these and that's why they're so helpful", "start": 2384.39, "duration": 5.3}, {"text": "yes", "start": 2386.69, "duration": 3.0}, {"text": "couldn't you just hide monads under the", "start": 2391.039, "duration": 4.601}, {"text": "covers and have a normal language well", "start": 2393.39, "duration": 4.139}, {"text": "it's really helpful to know where you", "start": 2395.64, "duration": 3.719}, {"text": "have effects and where you don't and", "start": 2397.529, "duration": 4.26}, {"text": "that's why it's very useful but in fact", "start": 2399.359, "duration": 5.01}, {"text": "indeed it's a current active area of", "start": 2401.789, "duration": 4.591}, {"text": "research how do you build the monads", "start": 2404.369, "duration": 5.19}, {"text": "into the language and in fact remember I", "start": 2406.38, "duration": 5.099}, {"text": "said look what's awful about this is you", "start": 2409.559, "duration": 3.78}, {"text": "have to rewrite the whole program and", "start": 2411.479, "duration": 3.63}, {"text": "what's great about monads is you don't", "start": 2413.339, "duration": 3.66}, {"text": "but notice that when you move from not", "start": 2415.109, "duration": 3.66}, {"text": "being in a monad to being in a monad", "start": 2416.999, "duration": 4.26}, {"text": "then you do so once you have to rewrite", "start": 2418.769, "duration": 4.23}, {"text": "the whole program into tedious but", "start": 2421.259, "duration": 3.72}, {"text": "straightforward way and after that you", "start": 2422.999, "duration": 4.171}, {"text": "don't maybe the language could do that", "start": 2424.979, "duration": 4.02}, {"text": "rewriting force itself if we're in a", "start": 2427.17, "duration": 2.78}, {"text": "monad or not", "start": 2428.999, "duration": 3.141}, {"text": "so in fact there's that's an active", "start": 2429.95, "duration": 4.26}, {"text": "subject of research but it's not made it", "start": 2432.14, "duration": 4.07}, {"text": "into mainstream languages yet", "start": 2434.21, "duration": 5.159}, {"text": "good question thank you question at the", "start": 2436.21, "duration": 5.339}, {"text": "back", "start": 2439.369, "duration": 2.18}, {"text": "okay so the question was state and", "start": 2461.54, "duration": 7.87}, {"text": "output look very similar and I think", "start": 2466.04, "duration": 6.01}, {"text": "you're sort of noticing that if you", "start": 2469.41, "duration": 4.86}, {"text": "never use the IMP if you just use the", "start": 2472.05, "duration": 4.2}, {"text": "output operation go to current state", "start": 2474.27, "duration": 4.2}, {"text": "that comes in and you ignore it and you", "start": 2476.25, "duration": 4.59}, {"text": "send it to what sorry you take it and", "start": 2478.47, "duration": 3.9}, {"text": "you append to it what you want", "start": 2480.84, "duration": 3.69}, {"text": "so just appending things to the output", "start": 2482.37, "duration": 3.87}, {"text": "all of it to the current state all the", "start": 2484.53, "duration": 3.93}, {"text": "time that is just like output so you", "start": 2486.24, "duration": 4.38}, {"text": "could actually define output on top of", "start": 2488.46, "duration": 5.04}, {"text": "state that is true I just want to give", "start": 2490.62, "duration": 5.55}, {"text": "you three examples of a monad and in", "start": 2493.5, "duration": 5.37}, {"text": "fact when you define output the way it's", "start": 2496.17, "duration": 4.41}, {"text": "done you can see the two computations", "start": 2498.87, "duration": 3.48}, {"text": "are independent you could do them in", "start": 2500.58, "duration": 3.9}, {"text": "either order as long as you print the", "start": 2502.35, "duration": 3.48}, {"text": "output of the first one before the", "start": 2504.48, "duration": 3.15}, {"text": "output of the second one so there's less", "start": 2505.83, "duration": 4.83}, {"text": "time dependence and it's easy easier to", "start": 2507.63, "duration": 5.43}, {"text": "make parallel the stuff with output than", "start": 2510.66, "duration": 4.26}, {"text": "the stuff with state so that's one", "start": 2513.06, "duration": 3.15}, {"text": "reason why you might want to use output", "start": 2514.92, "duration": 3.9}, {"text": "rather than state because it's easier to", "start": 2516.21, "duration": 4.44}, {"text": "see the stuff works in parallel that", "start": 2518.82, "duration": 3.3}, {"text": "there's no dependence between the two", "start": 2520.65, "duration": 4.02}, {"text": "parts excellent question", "start": 2522.12, "duration": 6.0}, {"text": "thank you so I said you could use monads", "start": 2524.67, "duration": 5.85}, {"text": "to do so much more I'm at the end of my", "start": 2528.12, "duration": 4.29}, {"text": "time so I'm just going to wave this in", "start": 2530.52, "duration": 3.33}, {"text": "front of you and saying among other", "start": 2532.41, "duration": 3.44}, {"text": "things you can do lists and streams and", "start": 2533.85, "duration": 4.74}, {"text": "so bind is just the thing you need if", "start": 2535.85, "duration": 3.79}, {"text": "you want something like Cartesian", "start": 2538.59, "duration": 3.51}, {"text": "products so here MFA needs a list or a", "start": 2539.64, "duration": 5.46}, {"text": "stream of a and Emma fee is the same and", "start": 2542.1, "duration": 5.97}, {"text": "we want to return a list or stream of Av", "start": 2545.1, "duration": 7.02}, {"text": "pairs so we just bind em to a and bind n", "start": 2548.07, "duration": 7.53}, {"text": "to be and pure an a/v pair and by the", "start": 2552.12, "duration": 6.24}, {"text": "way that's just like a for loop for each", "start": 2555.6, "duration": 5.4}, {"text": "a drone from M and each be drawn from n", "start": 2558.36, "duration": 9.75}, {"text": "yield a paired with B and Scala supports", "start": 2561.0, "duration": 10.08}, {"text": "the special for syntax for dealing with", "start": 2568.11, "duration": 4.83}, {"text": "lists or streams or other collections", "start": 2571.08, "duration": 4.71}, {"text": "and it is just a monad it's built on top", "start": 2572.94, "duration": 5.49}, {"text": "of monads and that means the same for", "start": 2575.79, "duration": 4.5}, {"text": "yield notation we could have used it to", "start": 2578.43, "duration": 4.23}, {"text": "rewrite all the evaluators I showed you", "start": 2580.29, "duration": 5.37}, {"text": "so instead of saying you know following", "start": 2582.66, "duration": 6.93}, {"text": "eval of whatever to a da da we could", "start": 2585.66, "duration": 4.5}, {"text": "just say", "start": 2589.59, "duration": 4.86}, {"text": "for a drawing from em okay so there's", "start": 2590.16, "duration": 7.619}, {"text": "nice syntax that supports monads and", "start": 2594.45, "duration": 5.01}, {"text": "they are useful for all sorts of things", "start": 2597.779, "duration": 4.441}, {"text": "including pretty much the most important", "start": 2599.46, "duration": 7.26}, {"text": "data structure in the world the list not", "start": 2602.22, "duration": 5.76}, {"text": "to mention it works just the same with", "start": 2606.72, "duration": 3.27}, {"text": "the second most important data structure", "start": 2607.98, "duration": 6.69}, {"text": "in the world the stream so let's", "start": 2609.99, "duration": 6.99}, {"text": "conclude we're on to the second part of", "start": 2614.67, "duration": 4.74}, {"text": "the definition of bone app monad noun to", "start": 2616.98, "duration": 5.73}, {"text": "our single-celled organism especially a", "start": 2619.41, "duration": 8.099}, {"text": "flageolet protozoan so we actually use", "start": 2622.71, "duration": 7.71}, {"text": "monads in the Haskell compiler so the", "start": 2627.509, "duration": 4.921}, {"text": "very first Haskell compiler was written", "start": 2630.42, "duration": 4.47}, {"text": "in Haskell and each baised used a monad", "start": 2632.43, "duration": 5.609}, {"text": "so the type inference phase had a monad", "start": 2634.89, "duration": 5.04}, {"text": "that dealt with exceptions and state and", "start": 2638.039, "duration": 5.28}, {"text": "read only state so output is sort of", "start": 2639.93, "duration": 5.429}, {"text": "write only state", "start": 2643.319, "duration": 4.29}, {"text": "you also need read only say first things", "start": 2645.359, "duration": 3.601}, {"text": "like your current location at which you", "start": 2647.609, "duration": 3.45}, {"text": "want to report an error so for each", "start": 2648.96, "duration": 4.53}, {"text": "phase of the compiler there was an", "start": 2651.059, "duration": 4.74}, {"text": "appropriate monad to use and if you", "start": 2653.49, "duration": 4.41}, {"text": "decided you needed more stuff it was", "start": 2655.799, "duration": 4.201}, {"text": "easy to change the Mon app so this", "start": 2657.9, "duration": 4.83}, {"text": "actually worked in practice and my first", "start": 2660.0, "duration": 4.71}, {"text": "day to talk this was the only evidence I", "start": 2662.73, "duration": 4.5}, {"text": "had that monads were a good idea and now", "start": 2664.71, "duration": 4.109}, {"text": "people have used it in many many many", "start": 2667.23, "duration": 3.18}, {"text": "ways and there's a little bit more", "start": 2668.819, "duration": 5.371}, {"text": "evidence that they're a good idea so as", "start": 2670.41, "duration": 7.26}, {"text": "was mentioned they're not my idea the", "start": 2674.19, "duration": 7.53}, {"text": "Eugenio Margie's idea he wrote a paper", "start": 2677.67, "duration": 6.899}, {"text": "in 1989 he was interested in", "start": 2681.72, "duration": 4.649}, {"text": "denotational semantics of programming", "start": 2684.569, "duration": 4.47}, {"text": "languages a bit of mathematical theory", "start": 2686.369, "duration": 4.47}, {"text": "and he noticed that when you do", "start": 2689.039, "duration": 3.931}, {"text": "denotational semantics of things like", "start": 2690.839, "duration": 5.101}, {"text": "exception state and output you had to", "start": 2692.97, "duration": 5.16}, {"text": "tediously rewrite the entire semantics", "start": 2695.94, "duration": 4.139}, {"text": "and that monads gave a nice way of", "start": 2698.13, "duration": 3.75}, {"text": "structuring things so you didn't need to", "start": 2700.079, "duration": 4.351}, {"text": "do that and I read his paper I thought", "start": 2701.88, "duration": 6.12}, {"text": "hey that will probably work for writing", "start": 2704.43, "duration": 5.97}, {"text": "programs as well so that was my", "start": 2708.0, "duration": 4.92}, {"text": "contribution was to take this theory", "start": 2710.4, "duration": 4.59}, {"text": "done by a true category theorist Eugenio", "start": 2712.92, "duration": 5.07}, {"text": "and explain it to haskell hackers and", "start": 2714.99, "duration": 5.039}, {"text": "then from there it got out into all", "start": 2717.99, "duration": 4.879}, {"text": "these other languages", "start": 2720.029, "duration": 2.84}, {"text": "by the way Michael Spivey had also", "start": 2723.21, "duration": 4.62}, {"text": "noticed the utility of monads for", "start": 2726.21, "duration": 3.66}, {"text": "exception handling although he didn't", "start": 2727.83, "duration": 3.87}, {"text": "notice its utility for anything else and", "start": 2729.87, "duration": 5.85}, {"text": "ten years earlier John Reynolds in the", "start": 2731.7, "duration": 5.67}, {"text": "paper called the essence of elavil had", "start": 2735.72, "duration": 3.48}, {"text": "come up with this idea of separating the", "start": 2737.37, "duration": 4.71}, {"text": "type int and the type M event oh yes mo", "start": 2739.2, "duration": 4.74}, {"text": "jennie-o did mathematics so it wasn't", "start": 2742.08, "duration": 5.52}, {"text": "called damn it was called T yes that", "start": 2743.94, "duration": 5.61}, {"text": "really is how big the difference between", "start": 2747.6, "duration": 8.04}, {"text": "mathematics and programming is so John", "start": 2749.55, "duration": 9.18}, {"text": "Reynolds had this idea of a cut of data", "start": 2755.64, "duration": 5.79}, {"text": "types and what he called phrase types so", "start": 2758.73, "duration": 4.11}, {"text": "these are what we've been calling values", "start": 2761.43, "duration": 3.99}, {"text": "and computations and he had the same", "start": 2762.84, "duration": 6.51}, {"text": "idea that into X sorry into int in this", "start": 2765.42, "duration": 7.62}, {"text": "case would become int 2 into X but he", "start": 2769.35, "duration": 5.37}, {"text": "didn't have these idea of what we've", "start": 2773.04, "duration": 7.35}, {"text": "been calling pure and bind we're out of", "start": 2774.72, "duration": 7.41}, {"text": "definitions of monad we're on to the", "start": 2780.39, "duration": 3.6}, {"text": "next word in the dictionary which is", "start": 2782.13, "duration": 5.0}, {"text": "monad ism or Mona dolla G noun", "start": 2783.99, "duration": 5.28}, {"text": "especially in the writings of Leibniz", "start": 2787.13, "duration": 5.2}, {"text": "the philosophical doctrine that monads", "start": 2789.27, "duration": 8.94}, {"text": "are the ultimate units of reality and I", "start": 2792.33, "duration": 9.44}, {"text": "will stop there thank you", "start": 2798.21, "duration": 3.56}, {"text": "actually I won't stop there the two", "start": 2807.6, "duration": 4.03}, {"text": "other important things to do the first", "start": 2809.68, "duration": 5.88}, {"text": "yep the first is to thank my colleagues", "start": 2811.63, "duration": 6.48}, {"text": "Toni Morris and Jed Wesley Smith they", "start": 2815.56, "duration": 5.07}, {"text": "helped produce all this Scala yesterday", "start": 2818.11, "duration": 6.72}, {"text": "Jed's n types of it a masterful effort", "start": 2820.63, "duration": 6.72}, {"text": "and he put all the source available up", "start": 2824.83, "duration": 4.26}, {"text": "here so you can just go there if you", "start": 2827.35, "duration": 4.68}, {"text": "want to actually run this and then", "start": 2829.09, "duration": 5.04}, {"text": "there's one last thing which I have to", "start": 2832.03, "duration": 5.13}, {"text": "do which is to just remind you right", "start": 2834.13, "duration": 6.0}, {"text": "when you've got a tough job apply the", "start": 2837.16, "duration": 5.75}, {"text": "right mathematics that is your candle", "start": 2840.13, "duration": 5.28}, {"text": "when you've got to write a tough job", "start": 2842.91, "duration": 4.6}, {"text": "what you should think is this is a job", "start": 2845.41, "duration": 5.96}, {"text": "for lambda calculus", "start": 2847.51, "duration": 3.86}]]