paren-free call expressions

Lasse Reichstein reichsteinatwork at gmail.com
Thu May 26 00:13:02 PDT 2011


On Thu, 26 May 2011 07:15:31 +0200, David Griffiths  
<dxgriffiths at gmail.com> wrote:

> Many, many languages (including Perl, Ruby, VB, Scala, Smalltalk,
> Logo, and of course all the ML-like languages, including Haskell and
> F#) do without parentheses for calls in some circumstances at least.
> Do you use any of these languages? I quite like some of them.

The functional languages (ML-like or Haskell-like) typicallly have curried  
function
definitions. I.e., if you define a function (ML-syntax, from memory :)
   let fun foo x y z = x * y * z
    in foo 2 3 4
   end;
the function foo isn't actually taking three arguments, it's a curried  
function of type
  int -> int -> int -> int
taking one argument and returning a new function.


You can also make one argument a product type, so:
   let fun bar (x, y) z = x * y * z
    in bar (2, 3) 4
   end;
defines a function of type (int * int) -> int -> int.

The point is that parentheses are not part of the call syntax at all. It's  
not that you can omit them in some
circumstances. You can omit them in all circumstances, because all  
functions take only *one argument*. That argument
might need to be a tuble, and you use parentheses to create tuples, but  
they don't need to be part of the call, e.g.
   let fun bar (x, y) z = x * y * z
       val tup = (2,3)
   in bar tup 4
   end;


ECMAScript doesn't curry its function declarations. A function does take  
all its arguments at once (and not as a
tuple value), and since we can even supply too few or too many arguments  
when calling a function, trying to
mimic SML will only bring pain.

Much as I like SML and Haskell, their function application syntax  
(literally "exp ::= exp_1 exp_2" [1]) just won't
work for ECMAScript. It's pretty in its simplicity, but ECMAScript is long  
past simplicity on this point.

/L
[1] First match for "SML grammar":  
http://www.mpi-sws.org/~rossberg/sml.html
-- 
Lasse Reichstein - reichsteinatwork at gmail.com


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