This I knew: Being UTF-8 and UTF-16 encodings, and because those encodings are variable-width, char[] and wchar[] cannot be RandomAccessRange ranges (dchar[] can be):

import std.range;

void main()
{
    assert(!isRandomAccessRange!( char[]));
    assert(!isRandomAccessRange!(wchar[]));
    assert( isRandomAccessRange!(dchar[]));
}

What I've recently discovered is that for being variable-width encodings, char[] and wchar[] cannot be used as OutputRange ranges either. This is because strings are ranges of Unicode characters in D, so their .front must return a dchar, and that dchar must be an rvalue in the cases of char[] and wchar[], which cannot be assigned to.

Only dchar[] has assignable elements:

import std.range;

void main()
{
    assert(!hasAssignableElements!( char[]));
    assert(!hasAssignableElements!(wchar[]));
    assert( hasAssignableElements!(dchar[]));
}

For that reason, only dchar[] can be used as OutputRange:

import std.range;

void main()
{
    assert(!isOutputRange!( char[],  char));
    assert(!isOutputRange!( char[], wchar));
    assert(!isOutputRange!( char[], dchar));

    assert(!isOutputRange!(wchar[],  char));
    assert(!isOutputRange!(wchar[], wchar));
    assert(!isOutputRange!(wchar[], dchar));

    assert( isOutputRange!(dchar[],  char));
    assert( isOutputRange!(dchar[], wchar));
    assert( isOutputRange!(dchar[], dchar));
}

Ali

char[] and wchar[] could still define a put method, which would make them output ranges.  This is worth a bug report.

"Ali Çehreli" <acehreli@yahoo.com> wrote in message news:jgh4a1$1286$1@digitalmars.com...
> This I knew: Being UTF-8 and UTF-16 encodings, and because those encodings are variable-width, char[] and wchar[] cannot be RandomAccessRange ranges (dchar[] can be):
>
> import std.range;
>
> void main()
> {
>     assert(!isRandomAccessRange!( char[]));
>     assert(!isRandomAccessRange!(wchar[]));
>     assert( isRandomAccessRange!(dchar[]));
> }
>
> What I've recently discovered is that for being variable-width encodings, char[] and wchar[] cannot be used as OutputRange ranges either. This is because strings are ranges of Unicode characters in D, so their .front must return a dchar, and that dchar must be an rvalue in the cases of char[] and wchar[], which cannot be assigned to.
>
> Only dchar[] has assignable elements:
>
> import std.range;
>
> void main()
> {
>     assert(!hasAssignableElements!( char[]));
>     assert(!hasAssignableElements!(wchar[]));
>     assert( hasAssignableElements!(dchar[]));
> }
>
> For that reason, only dchar[] can be used as OutputRange:
>
> import std.range;
>
> void main()
> {
>     assert(!isOutputRange!( char[],  char));
>     assert(!isOutputRange!( char[], wchar));
>     assert(!isOutputRange!( char[], dchar));
>
>     assert(!isOutputRange!(wchar[],  char));
>     assert(!isOutputRange!(wchar[], wchar));
>     assert(!isOutputRange!(wchar[], dchar));
>
>     assert( isOutputRange!(dchar[],  char));
>     assert( isOutputRange!(dchar[], wchar));
>     assert( isOutputRange!(dchar[], dchar));
> }
>
> Ali