There are a lot of algorithms in std.algorithm that operate on
"foo(Range, Needles...)(Range range, Needles needles)".
Needles can be anything, in particular, either an "element" or a
"range".
The thing is that every now and then, you want to save the
entirety of (the ranges) inside needles. EG, I want to be able to
write:
foo(range, needles.saveAll);
I'm having trouble. I did two iterations:
//----
auto saveAll(Ranges...)(Ranges ranges) @property
{
auto ret = ranges;
foreach (Index, Type; Ranges)
static if (isForwardRange!Type)
ret[Index] = ranges[Index];
return ret;
}
//----
This doesn't work, because: Error: functions cannot return a tuple
So that's that.
The next try was:
//----
void saveAll(Ranges...)(in Ranges iRanges, ref Ranges oRanges)
@property
{
TypeTuple!Ranges ret = ranges;
foreach (Index, Type; Ranges)
static if (isForwardRange!Type)
ret[Index] = ranges[Index];
return ret;
}
//----
This doesn't either, because a function can't have double varargs
arguments. It's ambiguous...
So this left me with the option of just inlining into the code:
//----
Needles savedNeedles = needles;
foreach (Index, Type; Needles)
static if (isForwardRange!Type)
savedNeedles[Index] = needles[Index];
size_t r = startsWith!pred(haystack, savedNeedles);
//----
It works, but is kind of ugly, I'd have really wanted to be able
to just write:
//----
size_t r = startsWith!pred(haystack, needles.saveAll);
//----
Any thought on how do get this working?
