#Monoid in Scala by programmers from different backgrounds#
In spirit of The Evolution of a Haskell Programmer. Originally stolen from isoresursive.
George Leontiev folone
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| > effect/console | |
| [warn] Credentials file /home/folone/.ivy2/.credentials does not exist | |
| [warn] Credentials file /home/folone/.ivy2/.credentials does not exist | |
| [info] Starting scala interpreter... | |
| [info] | |
| Welcome to Scala version 2.9.2 (OpenJDK 64-Bit Server VM, Java 1.7.0_21). | |
| Type in expressions to have them evaluated. | |
| Type :help for more information. | |
| scala> import scalaz._, Scalaz._, effect._ |
folone
/ gist:5320098
Last active
December 15, 2015 20:40
Fooling around with State, defined as a monad of Adjunction[Writer, Reader], as per http://stackoverflow.com/a/4702513/163423
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| > core/console | |
| [warn] Credentials file /home/folone/.ivy2/.credentials does not exist | |
| [info] Starting scala interpreter... | |
| [info] | |
| Welcome to Scala version 2.9.2 (OpenJDK 64-Bit Server VM, Java 1.7.0_17). | |
| Type in expressions to have them evaluated. | |
| Type :help for more information. | |
| scala> import scalaz._ | |
| import scalaz._ |
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| BUILD SUCCESSFUL | |
| Total time: 9 minutes 21 seconds | |
| Welcome to Scala version 2.11.0-20130329-204437-40d2981c24 (OpenJDK 64-Bit Server VM, Java 1.7.0_17). | |
| Type in expressions to have them evaluated. | |
| Type :help for more information. | |
| scala> :kind scala.Option | |
| Option's kind is * -> * | |
| scala> :k scalaz.Unapply |
folone
/ kind.scala
Last active
February 20, 2018 22:18
— forked from eed3si9n/kind.scala
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| // Updated for Scala 2.10.0. | |
| def kind[A: scala.reflect.runtime.universe.TypeTag](a: A): String = { | |
| import scala.reflect.runtime.universe._ | |
| def typeKind(sig: Type): String = sig match { | |
| case PolyType(params, resultType) => | |
| (params map { p => | |
| typeKind(p.typeSignature) match { | |
| case "*" => "*" | |
| case s => "(" + s + ")" | |
| } |
folone
/ isomonoid.scala
Last active
December 15, 2015 07:39
Monoid instance throught an isomorphism
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| scala> import scalaz._ | |
| import scalaz._ | |
| scala> import std.option.optionFirst | |
| import std.option.optionFirst | |
| scala> import syntax.monoid._ | |
| import syntax.monoid._ | |
| scala> import Isomorphism._ |
folone
/ adjunction.scala
Last active
December 15, 2015 07:18
- Things, that can be described as Adjunctions
- Things, that can be described as Cofree
- Things, that can be described as Free monads, inspired by http://yow.eventer.com/yow-2012-1012/lambda-the-ultimate-dependency-injection-framework-by-runar-bjarnason-1277
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| type State[E] = Adjunction[({type λ[α] = Writer[E, α]})#λ, ({type λ[α] = Reader[E, α]})#λ] | |
| type Store[E] = Adjunction[({type λ[α] = Reader[E, α]})#λ, ({type λ[α] = Writer[E, α]})#λ] | |
| type Cont = Adjunction[Function0, Function0] // Function0 -| Function0 |
folone
/ gist:4946543
Last active
December 13, 2015 17:18
Hanoi towers at compile time become very easy with dependent types.
https://gist.github.com/travisbrown/3772462
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| > shapeless-core/console | |
| [warn] Credentials file /home/folone/.ivy2/.credentials does not exist | |
| [info] Compiling 24 Scala sources to /home/folone/workspace/shapeless/core/target/scala-2.11/classes... | |
| [info] Starting scala interpreter... | |
| [info] | |
| Welcome to Scala version 2.11.0-20130205-141957-132e09fc2e (OpenJDK 64-Bit Server VM, Java 1.7.0_09). | |
| Type in expressions to have them evaluated. | |
| Type :help for more information. | |
| scala> import shapeless.SingletonTypes._ |
folone
/ gist:4945168
Last active
April 27, 2017 13:10
A taste of dependent types in scala with shapeless.
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| > shapeless-core/console | |
| [warn] Credentials file /home/folone/.ivy2/.credentials does not exist | |
| [info] Compiling 24 Scala sources to /home/folone/workspace/shapeless/core/target/scala-2.11/classes... | |
| [info] Starting scala interpreter... | |
| [info] | |
| Welcome to Scala version 2.11.0-20130205-141957-132e09fc2e (OpenJDK 64-Bit Server VM, Java 1.7.0_09). | |
| Type in expressions to have them evaluated. | |
| Type :help for more information. | |
| scala> import shapeless._ |
folone
/ gist:4729451
Last active
December 12, 2015 06:28
Dependent types in scala.
https://github.com/milessabin/shapeless/blob/topic/macro-paradise/core/src/main/scala/shapeless/snat.scala
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| shapeless [0849b6f...] % sbt | |
| [info] Loading project definition from /home/folone/workspace/shapeless/project | |
| [info] Set current project to shapeless (in build file:/home/folone/workspace/shapeless/) | |
| > shapeless-core/console | |
| [warn] Credentials file /home/folone/.ivy2/.credentials does not exist | |
| [info] Compiling 2 Scala sources to /home/folone/workspace/shapeless/core/target/scala-2.11/classes... | |
| [info] Compiling 24 Scala sources to /home/folone/workspace/shapeless/core/target/scala-2.11/classes... | |
| [info] Starting scala interpreter... | |
| [info] | |
| Welcome to Scala version 2.11.0-20130205-141957-132e09fc2e (OpenJDK 64-Bit Server VM, Java 1.7.0_09). |