Why is std.algorithm.reduce impure?

[Adam D. Ruppe]

On Tuesday, 6 March 2012 at 22:48:30 UTC, H. S. Teoh wrote:
> Oh? what's wrong with the const?

test10.d(3): Error: function test10.product without 'this' cannot 
be const/immutable

It works if you put parens on it:

         pure const(int) product(int[] args) {


Without the parenthesis, D wants to apply it to this,
like if you write void foo() const {} in C++.

The reason here is most the attributes are at the
beginning, which is cool because this works:

const {
   void foo() {}
   int bar() {}
}

etc.


But if you put parens on it, it specifically applies
to the int.