[Issue 4264] Various std.algorithm.map problems

[d-bugmail at puremagic.com]

http://d.puremagic.com/issues/show_bug.cgi?id=4264



--- Comment #4 from yebblies <yebblies at gmail.com> 2010-07-16 21:17:49 PDT ---
(In reply to comment #3)
> 
> But this too doesn't work:
> 
> import std.algorithm, std.conv, std.range;
> void main() {
>     auto r1 = map!(to!(string, uint))(iota(20));
> }
> 
> 
> import std.algorithm, std.conv, std.range;
> void main() {
>     auto r1 = map!(to!(string, int))(iota(20));
> }
> 

You're right.  But this is not a problem with map, I think this is bug337.

void t1(U = int)(int a)
{
}
void t1(U = int)()
{
}
void t2(U = int, T = int)(int a)
{
}
void t2(U = int, T = int)()
{
}

void main() {
    t1!()(1); // works
    t1!()(); // works
    t1!(int)(1); // fails
    t1!(int)(); // fails
    t2!()(1); // works
    t2!()(); // works
    t2!(int)(1); // works
    t2!(int)(); // works
    t2!(int,int)(1); // fails
    t2!(int,int)(); // fails
}

It can probably be worked around by combining the radix and non-radix form of
to!(string,int).
Maybe a separate bug?



> If you perform a map! on an iterable that has a length, then map! detects it at
> compile-time and offers a length attribute, otherwise it's not offered.
> 
> So map! and other similar higher order functions can adapt and offer as much as
> possible.
> 
> If the iterable given to map! has just an opApply, then map! can offer just an
> opApply, for an iteration that can't be resumed.

Ok, I see your point, but if map is going to work with opApply it will no
longer be able to provide the standard range interface.
Either way this is an enhancement request and not a bug.

map!func(structWithOpApply) would also no longer work with most of
std.algorithm without extensive (and maybe impossible) modifications.



> array() can work with anything that can be iterated by foreach.

Agreed.
array() is special in that it always evaluates the entire range immediately.

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