Idea: Introduce zero-terminated string specifier

[Johannes Pfau]

Am Mon, 01 Oct 2012 13:22:46 +0200
schrieb Piotr Szturmaj <bncrbme at jadamspam.pl>:

> Paulo Pinto wrote:
> > On Monday, 1 October 2012 at 09:42:08 UTC, Piotr Szturmaj wrote:
> >> Jakob Ovrum wrote:
> >>> On Monday, 1 October 2012 at 09:17:52 UTC, Piotr Szturmaj wrote:
> >>>> Adam D. Ruppe wrote:
> >>>>> On Saturday, 29 September 2012 at 02:11:12 UTC, Alex Rønne
> >>>>> Petersen wrote:
> >>>>> Also this reminds me of the utter uselessness of the current
> >>>>> behavior of
> >>>>> "%s" and a pointer - it prints the address.
> >>>>
> >>>> Why not specialize current "%s" for character pointer types so
> >>>> it will print null terminated strings? It's always possible to
> >>>> cast to void* to print an address.
> >>>
> >>> It's not safe to assume that pointers to characters are generally
> >>> null terminated.
> >>
> >> Yes, but programmer should know what he's passing anyway.
> >
> > The thinking "the programmer should" only works in one man teams.
> >
> > As soon as you start having teams with disparate programming
> > knowledge among team members, you can forget everything about "the
> > programmer should".
> 
> I experienced such team at my previous work and I know what you mean.
> My original thoughts was based on telling writef that I want print a 
> null-terminated string rather than address. to!string will surely
> work, but it implies double iteration, one in to!string to calculate
> length (seeking for 0 char) and one in writef (printing). With long
> strings this is suboptimal. What about something like this:
> 
> struct CString(T)
>      if (isSomeChar!T)
> {
>      T* str;
> }
> 
> @property
> auto cstring(S : T*, T)(S str)
>      if (isSomeChar!T)
> {
>      return CString!T(str);
> }
> 
> string test = "abc";
> immutable(char)* p = test.ptr;
> 
> writefln("%s", p.cstring); // prints "abc"
> 
> Here the char pointer type is "annotated" as null terminated string
> and writefln can use this information.

If CString implemented a toString method (probably the variant taking a
sink delegate), this would already work. I'm not sure about performance
though: Isn't writing out bigger buffers a lot faster than writing
single chars? You could print every char individually, but wouldn't a
p[0 .. strlen(p)] usually be faster?