[Haskell-beginners] can I use "pure" all the time instead of "return" now?

Silent Leaf silent.leaf0 at gmail.com
Sun May 15 15:39:39 UTC 2016

Typo, I wrote:
>  as in "non-monadic values are impure"
meant of course
>  as in "monadic values are impure"

Le dimanche 15 mai 2016, Silent Leaf <silent.leaf0 at gmail.com> a écrit :
> Interesting interpretation!
> It might not be the one intended, but I always saw "pure" as meaning
something like "input just wrapped" (echoing Maybe ofc), "input without
effects", i think is the terminology. In other terms, to me "pure", there,
is not an absolute description of the "type" of input (especially since the
name of a function traditionally mostly defines the output, not the input),
as in "non-monadic values are impure", but is a relative description
visavis the input, aka, "the output is the undiluted, uneffectful monadic
version of the input". Dunno if that was what you meant by "unadorned".
> In other terms "pure" makes me see the function as a sort of identity
that does not dilute or otherwise modify the input value, solely "wraps" it
(more or less metaphorically), makes it monadic without modification. I
don't see it as meaning that its input values are of a purer "kind" than
the corresponding outputs because those latter are (more) monadic. And we
can feed monadic values to pure anyway.
> As for echoing "purely functional language", well ... i don't really see
the link (but i might very well miss something), but at any rate isn't it
true in the first place (Haskell being pure, barring uses of
> Le dimanche 15 mai 2016, Doug McIlroy <doug at cs.dartmouth.edu> a écrit :
>>>  the name [return] "stains" the functional semantics in Monadic code,
>>> in my opinion
>> Amusing. For me, the term "pure" stains monads as impure or diluted.
>> The moral overtones of "pure", as in "purely functional language",
>> drive out more benign interpretatations such as "unadorned". Not
>> a felicitous coinage.
>> Doug McIlroy
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