2008/4/1, Jules Bean
PR Stanley wrote:
Why can't we have function application implemented outwardly (inside-out).
No reason we can't.
We could.
We just don't.
People have spent some time thinking and experimenting and have decided this way round is more convenient. It's certainly possible to disagree.
I bet this "time and thinking" involved currying. For instance, with: f :: int -> int -> int f a b = a + b + 3 Let's explore the two possibilities (1) f 4 2 <=> (f 4) 2 -- don't need parentheses (2) f 4 2 <=> f (4 2) -- do need parentheses: (f 4) 2 Curried functions are pervasive, so (1) just saves us more brakets than (2) does.
f g x returns an error because f takes only one argument.
Do not forget that *every* function take only one argument. The trick is that the result may also be a function. Therefore, f g 5 <=> id id 5 <=> (id id) 5 <=> id 5 <=> 5 indeed do run smoothly (just checked in the Ocaml toplevel, thanks to Jerzy for pointing this out). Loup