isAsciiString in Phobos?

[Andrej Mitrovic]

On 10/7/13, Adam D. Ruppe <destructionator at gmail.com> wrote:
> If you want strict ASCII, it should be <= 127 rather than 255
> because the high bit can be all kinds of different encodings (the
> first 255 of unicode codepoints I think match latin-1
> numerically, but that's different than windows-1252 or various
> non-English extended asciis.)
>
> You could also convert utf-8 to ascii.... sort of... by just
> stripping out any byte > 127 since bytes higher than that are
> multibyte sequences in utf8.

Thanks. I got some useful info from Jakob from IRC, and ended up with this:

bool isAsciiString(string input)
{
    auto data = cast(const(ubyte)[])input;
    return data.all!(a => a <= 0x7F);
}

The cast is needed to avoid decoding by the "all" function. Also
there's isASCII that works on a dchar in std.ascii, but I was looking
for something that works on entire strings at once. So the above
function does the work for me.

Should we put something like this in Phobos?