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0 pointscatnaroek10y ago0 comments

I'd distinguish between (at least) three degrees of “purity”:

(0) Absolutely anything goes. Examples: Racket (in the REPL), Lisp, Clojure, Scala, Erlang, etc.

(1) Values are immutable, but any computation might have any effect. Examples: Standard ML, OCaml (mostly), Racket (mostly).

(2) Values are immutable, and computations are type-annotated with their possible effects. Examples: Haskell, Idris, Ur/Web.

0 comments

i_s10y ago

Pretty strange that you put Clojure in the "anything goes" category when it has been the clear leader when it comes to immutability. Lots of those languages you put in the other categories don't even have persistent data structures in their standard library.

catnaroekOP10y ago

Here is why: http://pastebin.com/t3Q3CW4j

This is particularly infuriating because the proper way to handle bound variables is already known: https://en.wikipedia.org/wiki/De_Bruijn_index .

2 more replies

rdtsc10y ago

> Absolutely anything goes. Examples: Racket (in the REPL), Lisp, Clojure, Scala, Erlang, etc.

Well you can't mutate variables and data in Erlang. (Try X=1,X=2 in a repl, it will fail). There is a thing called process dictionary but it is frowned upon. Concurency is handled by processes. But that's a different thing.

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