Improvements to hasSlicing #854

…ngth." This reverts commit 6a0b6c4.

takeExactly now returns the same type as take where possible, and neither take nor takeExactly check hasSlicing for infinite ranges (since infinite ranges will soon be required to use them for slicing, and that creates a circular dependency among those 3 templates

Now, it enforces that opSlice returns a range which can be assigned to the original range type (so that it can be assigned to the original range as long as the original range isn't const) as long as it's finite, and it enforces that opSlice's result is the result of take when the range is infinite.

import std.algorithm; import std.range; void main() { auto N2 = sequence!"n"(cast(size_t)1).map!"a"; } ceased to compile, because Map's opSlice won't work anymore over infinite ranges, because the result can't be reassigned to the original.

Ideally, opDollar would be outright required for any range with slicing, but unless/until it's changed so that length automatically aliases to opDollar when opDollar isn't defined (issue# 7177), that's probably not a reasonable requirement to make.

The extra requirements are not currently enabled because of bug# 8847, but they're now there, and they're listed as their in the documentation so that no one will think that they're not supposed to apply.

It now requires that indexing with $ result in the same type as front if r[$] works, and if that works, and the range isn't infinite, r[$ - 1] must be the same type as front. Ideally, we'd require that r[$] work regardless, but without enhancement dlang#7177 being implemented, that would likely break too much code, as opDollar was only recently fixed and probably isn't used much.

They were removed previously but reintroduced due to a bad rebase, so I'm removing them again here.

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Improvements to hasSlicing #854

Improvements to hasSlicing #854

Commits on Dec 17, 2012