> On 10 Feb 2024, at 09:06, Al <frm...@mailgw.com> wrote: > > >>> * only side-effect free, or ... >>> >>> * also return the same value when called with the same arguments? >> >> The first implies the second: to be able to choose from a set of return >> values for the same given argument, you do need to have side-effects, e.g., >> interact with a RNG which maintains state, read from a file, maintain an >> index into a circular vector of results, etc.. >> >> Here's what the docs say: >> http://wiki.call-cc.org/man/5/Declarations#pure >> > "referentially transparent, that is, as not having any side effects". You can > read "the environment" (including all globals) without actually modifying the > environment. Between two applications of the procedure, other impure > procedures may modify the environment. So it's not clear if it means Haskell > monad purity or immutable purity, hence my question.
I don't get your question: those two things are the same thing :) Referential transparency means you can substitute an expression with its expansion down to a value. If anything happening in between causes (observable *) changes, you can't do it anymore. (*) modifying the program counter is not an observable change, for example. -- Pietro Cerutti I've pledged to give 10% of income to effective charities and invite you to join me. https://givingwhatwecan.org Sent from a small device - please excuse brevity and typos.
