Apropos March 10, 2021

00 Show notes.md

Show Notes

Topics

Follow-up on tagged literals from last episode

Tagged Literal type (added Clojure 1.8, 2018): https://insideclojure.org/2018/06/21/tagged-literal/

(set! *default-data-reader-fn* tagged-literal)

Malli

https://github.com/metosin/malli

Update on Grokking Simplicity (Eric's book)

• Link: https://lispcast.com/gs

Dynamically implementing protocols

• Tweet from @puredanger (Alex Miller): https://twitter.com/puredanger/status/1368949555945893890
• Link from Tommi Reiman: https://github.com/metosin/malli/blob/master/src/malli/core.cljc#L295-L308

REPL Time!!

• Problem link: https://gist.github.com/ericnormand/c9056ff19a066038137f60dd4c28ac6e

Pattern matching

When describing rhyming patterns, poets use letters to define patterns, like this:

Roses are red A
Violets are blue B
Sugar is sweet C
and so are you B

This poem has an ABCB rhyming structure because the B lines rhyme and A and C do not.

We'll use this same naming scheme but use equality instead of rhyming. Write a function that takes a sequence of values and a pattern string. It returns a a map of letters to values if the pattern matches, and nil if it does not.

Examples:

(pattern [1 2 1 2] "ABAB") ;=> {\A 1 \B 2}
(pattern [1 2 3 2] "ABCB") ;=> {\A 1 \B 2 \C 3}
(pattern [1 2 3 4] "ABAB") ;=> nil
(pattern [1 1 1 1] "A") ;=> nil (wrong number of elements)
(pattern [1 1 1 1] "ABCD") ;=> {\A 1 \B 1 \C 1 \D 1}
(pattern [1 4 2 1] "ADCA") ;=> {\A 1 \D 4 \C 2}

Where to join us

Discord - Join if you want to watch us live or chat! https://discord.com/invite/hGNnK8N

Recording and playback on YouTube - https://www.youtube.com/channel/UC1UxEQuBvfLJgWR5tk_XIXA

Follow us on Twitter for updates - https://twitter.com/AproposClj

Love the show. Two concerns:

1. Spec is ultimately aimed at fine-grained dependencies. It frustrates me when whole conversations go on without that being said.
2. Rich has said mea culpa. It's the point of his talk "Maybe Not".