On Thu, 19 May 2011 10:14:58 -0400, Lars Tandle Kyllingstad
<[email protected]> wrote:
Below is a simple implementation of a range which iterates another
(input) range by reference, for those cases when using an
InputRangeObject is overkill. I've used it quite a bit and I find it
immensely useful.
It is sort of the opposite of save(). Where save() ensures that you are
only consuming a copy of the original range, byRef() ensures that you
are consuming the original range.
Would this be useful for Phobos? I guess it is a tad unsafe, since it
stores the address of the range, which may well be stored on the stack.
/** Range that iterates another range by reference. */
auto byRef(Range)(ref Range range) if (isInputRange!Range)
{
static struct ByRef
{
private Range* _range;
static if (isInfinite!Range)
{
enum empty = false;
}
else
{
@property bool empty() { return (*_range).empty; }
}
@property ElementType!Range front()
{
return (*_range).front;
}
void popFront()
{
(*_range).popFront();
}
}
return ByRef(&range);
}
unittest
{
auto a = [1, 2, 3, 4];
auto b = take(byRef(a), 2);
assert (equal(b, [1, 2]));
assert (equal(a, [3, 4]));
}
I've wrote version of this for my Json library, so yes, I think it's
useful. I'd recommend a few things. First, if the Range is a reference
type, then you don't need the extra level of indirection. Second, you may
wish to include the rest of the range primitives, plus length/slicing, if
the base type supports them.
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