On 11/30/2011 11:46 AM, Steven Schveighoffer wrote:
On Wed, 30 Nov 2011 10:54:11 -0500, Xinok <xi...@live.com> wrote:
On 11/30/2011 7:50 AM, Steven Schveighoffer wrote:
On Tue, 29 Nov 2011 15:06:11 -0500, Jonathan M Davis
<jmdavisp...@gmx.com> wrote:
The type of the index should be irrelavent to the underlying loop
mechanism.
Note that the issue is really that foreach(T i, val; arr) {...}
translates to for(T i = 0; i < arr.length; ++i) {auto val = arr[i]; ...}
Why can't it be (aside from the limitation in for-loop syntax, but you
get the idea): for(size_t _i = 0, T i = _i; _i < arr.length; i = ++_i)
{auto val = arr[_i]; ...}
Same issue with foreach(i; -10..10), what if I wanted to do foreach
(ubyte i; ubyte.min..ubyte.max + 1). This should not result in an
infinite loop, I should be able to use foreach to iterate all the values
of ubyte. The compiler should just "figure out" how to do it right.
-Steve
This actually doesn't compile:
foreach (ubyte i; ubyte.min..ubyte.max + 1)
Error: cannot implicitly convert expression (256) of type int to ubyte
It's a little more to type, but just write a property which does an
explicit cast:
foreach(_i; ubyte.min .. ubyte.max + 1){
ubyte i(){ return cast(ubyte)_i; }
}
This is hugely inefficient...
foreach(_i; ubyte.min..ubyte.max + 1){
ubyte i = cast(ubyte)_i;
}
But my point was, foreach over a range gives me all the elements in a
range, regardless of how the underlying loop is constructed. The
limitation by the compiler is artificial.
I remember at one point there was someone who had actual code that
resulted in a loop for ubytes, or was trying to figure out how to
foreach over all possible ubyte values.
-Steve
It shouldn't be. The compiler should be smart enough to inline the
function and optimize the typecast to something like this:
void main(string[] args){
foreach(_i; ubyte.min .. ubyte.max + 1)
writeln(*cast(ubyte*)&_i);
}
This would actually be faster since you don't have to iterate two variables.
