• BCS <ao pathlink.com> May 01 2007
• Daniel Keep <daniel.keep.lists gmail.com> May 01 2007
• BCS <ao pathlink.com> May 01 2007

BCS <ao pathlink.com> writes:

I have a template

int Foo(T)(T bar);

I want to be able to call it like this:

foo("hello");

and have T end up as char[] not char[5]. Is there any way to limit the template 
to that?

Daniel Keep <daniel.keep.lists gmail.com> writes:

BCS wrote:
 I have a template
 
 int Foo(T)(T bar);
 
 I want to be able to call it like this:
 
 foo("hello");
 
 and have T end up as char[] not char[5]. Is there any way to limit the
 template to that?


Not one that I can think of off the top of my head.  The problem is that
you can't specialise templated functions.

That said, you might be able to do something like this (note: untested,
off the top of my head code):

template Foo(T)
{
    static if( IsStaticArray!(T) )
        alias Foo!(DynamicArrayFromStaticArray!(T)) Foo;
    else
        int Foo(T bar)
        {
            ...
        }
}

Obviously, you'd have to write IsStaticArray and
DynamicArrayFromStaticArray (unless they're in std.traits).

The other thing you can do is ensure the argument is really a char[] in
the first place:

foo("hello"[]);

The [] does a slice of the char[5], which results in a char[].

	-- Daniel

-- 
int getRandomNumber()
{
    return 4; // chosen by fair dice roll.
              // guaranteed to be random.
}

http://xkcd.com/

v2sw5+8Yhw5ln4+5pr6OFPma8u6+7Lw4Tm6+7l6+7D
i28a2Xs3MSr2e4/6+7t4TNSMb6HTOp5en5g6RAHCP  http://hackerkey.com/

BCS <ao pathlink.com> writes:

Reply to Daniel,

 BCS wrote:
 
 I have a template
 
 int Foo(T)(T bar);
 
 I want to be able to call it like this:
 
 foo("hello");
 
 and have T end up as char[] not char[5]. Is there any way to limit
 the template to that?
 


 that you can't specialise templated functions.
 


Am I not understanding you correctly, I thought this worked (it did the last 
time I checked)

int bar(char[] s: "hello")()
{
return s.length;
}

I though of that, but what I going for is code folding to reduce duplication.

I just though of what to do

int FooT(T)(T bar);
alias FooT!(char[]) Foo;
alias FooT!(int) Foo;

this works because I have a finite list of type that are to be allowed.

The "good" way to do it would be to allow for limiting rules to be applied:

int foo(T : is(T[]) || !is(T.length)]) ;