On 03/03/2012 05:57 AM, Piotr Szturmaj wrote:
> Consider a custom range of
> char:
>
> struct CharRange
> {
> @property bool empty();
> @property char front();
> void popFront();
> }
>
> typeof(CharRange.front) and ElementType!CharRange both return _char_
Yes, and I would expect both to the same type.
> while for string they return _dchar_. This discrepancy pushes the range
> writer to handle special string cases.
Yes, Phobos faces the same issues.
> I'm currently trying to write
> ByDchar range:
>
> template ByDchar(R)
> if (isInputRange!R && isSomeChar!(ElementType!R))
> {
> alias ElementType!R E;
> static if (is(E == dchar))
> alias R ByDchar;
> else static if (is(E == char))
> {
> struct ByDchar
> {
> ...
> }
> }
> else static if (is(E == wchar))
> {
> ...
> }
> }
>
> The problem with that range is when it takes a string type, it aliases
> this type with itself, because ElementType!R yields dchar. This is why
> I'm talking about "bad consequences", I just want to iterate string by
> _char_, not _dchar_.
In case you don't know already, there are std.traits.isNarrowString,
std.range.ForEachType, etc. which may be useful.
Ali
