foreach

[Jarrett Billingsley]

On Sun, Nov 23, 2008 at 10:48 AM, Sam S E <asdf at mailinator.com> wrote:
> Jarrett Billingsley Wrote:
>
>> On Sat, Nov 22, 2008 at 11:40 PM, Sam S E <eisenstat.aa at sympatioco.ca> wrote:
>> > Does foreach use delegates? Isn't that unnecessary overhead?
>> > --Sam
>>
>> It does use delegates, for iterating over most types.  When iterating
>> over arrays, the compiler turns it into a sort of for loop instead.
>>
>> Is it unnecessary overhead?  It's not always as fast as it could be,
>> but unless someone can figure out some other way of implementing it,
>> it's pretty much the best we can get.
>>
>> How about iterator objects, like in C++ or Java?  Are they unnecessary
>> overhead?  ;)
>
> Why not just use a normal for loop; wouldn't it be almost as simple as token substitution? By 'most types,' do you mean associative arrays or am I forgetting something? As a mainly C(++) programmer, I don't use iterators when I don't need to. I don't even use classes when I don't need to.

How do you use a for loop to iterate over an associative array whose
implementation is hidden, or a binary tree, or any arbitrary
container, or a sequence or words in a file, or the zipped contents of
two lists, or...

The point of foreach isn't performance, it's flexibility and
abstraction.  As long as you can make an opApply or function which
takes a delegate, you can use the foreach loop with it.  Not
everything is an array.