About std.ascii.toLower

[monarch_dodra]

On Friday, 21 September 2012 at 10:45:42 UTC, Jonathan M Davis 
wrote:
> On Friday, September 21, 2012 12:38:07 monarch_dodra wrote:
>> On Friday, 21 September 2012 at 10:23:39 UTC, Jonathan M Davis
>> 
>> wrote:
>> > On Friday, September 21, 2012 11:00:31 monarch_dodra wrote:
>> >> What do you (you two) think of my proposition for a
>> >> "std.strictascii" module?
>> > 
>> > I don't think that it's at all worth it. It's just duplicate
>> > functionality in
>> > order to avoid a cast.
>> 
>> (and contract)
>
> If that's what you want, it's easy enough to create a helper 
> function which
> you use instead of a cast which does the contract check as 
> well. e.g.
>
> char toChar(dchar c)
> {
>     assert(isAscii(c));
>     return cast(char)c;
> }
>
> foreach(ref char c; str)
>     c = toChar(std.ascii.toLower(c));
>
> It should be completely optimized out with -release and -inline.
>
> - Jonathan M Davis

That's a real good idea. Also, I find it is these kinds of 
situations where UFCS really shines (IMO):

     foreach(i, c; s1)
         cs[i] = c.toUpper().toChar();

I love this syntax.

Related, could "toChar" be considered for inclusion? I think it 
would be a convenient tool for validation.

/*
  * Casts dchar to a char.
  *
  * Preconditions:
  *   $(D c) must be representable in a single char.
  */
char toChar(dchar c)
{
     assert(c < 256, "toChar: Input too large for char");
     return cast(char)c;
}

That said, if we go that way, we might as well just have a more 
generic safeCast in std.conv or something:

T safeCast(T, U)(U i)
     if(isBasicType!T && isBasicType!U)
{
     assert(cast(T)i == i, "safeCast: Cast failed");
     return cast(T)i;
}

     foreach(i, c; s1)
         cs[i] = c.toUpper().safeCast!char();

Hum... yeah... I don't know...

I seem to be typing faster than I can really think of the 
consequences of such a function.