RE: [Caml-list] ReasonML concrete syntax

[David Allsopp <dra-news@metastack.com>]

Evgeny Khramtsov wrote:
> Wed, 13 Dec 2017 09:22:05 +0100
> Sebastien Ferre <Sebastien.Ferre@irisa.fr> wrote:
> 
> > They have two notations, f(x,y) and f(x)(y), the latter being the
> > curryfied version allowing partial application.
> 
> This is too complex for JavaScript developers.

Speaking as (I think) OCaml's only Windows-by-preference core developer, a sometime viola player[1], a countertenor[2], a sometime "expert" Visual Basic developer, one who has written quite a lot of ML and quite a lot of non-trivial JavaScript, and probably holder of many other oft-insulted categories, may I observe that in the archives of these threads, it's rare that the ones hurling the insults paint the greatest pictures of either their arguments or themselves...

One of the many differences between the Standard ML basis library and OCaml's stdlib which I find interesting is that SML typically eschews currying unless it's clearly beneficial, preferring signatures like 'a * 'b -> 'c unless 'a -> 'b -> 'c is clearly useful. Standard ML also has stricter rules on the parentheses for tuples, of course.

In terms of why you might want to be "hiding" currying, or at least making it need less immediate explanation when learning the language, consider, for example, explaining the difference between:

let f x y = print_int x; print_int y in
f 42

and

let f x = print_int x; print_int in
f 42

(I'm guessing with its web-based heritage that Reason programming involves a few side-effects)

From my limited experience of teaching beginners to ML - both those who have programmed and those who haven't - I'd say that currying is probably one of the concepts requiring the most explanation; certainly much more than call-by-value vs lazy, or even immutable values. I can certainly see why the Reason team are doing so much to try to make it seem more familiar.


David


[1] https://en.wikipedia.org/wiki/Viola_jokes
[2] http://myweb.tiscali.co.uk/stnicolaschurch/mus-altos.html