Re: Template trouble

• Subject: Re: Template trouble
• From: Steve Checkoway <email@hidden>
• Date: Mon, 28 Aug 2006 17:11:53 -0700
• Delivered-to: email@hidden
• Delivered-to: email@hidden

On Aug 28, 2006, at 1:00 PM, Edward K. Chew wrote:

Oh, I forgot to mention, I have run into trouble with template specialization. For example, I have a function along the lines:

template <typename T> UInt32 myHashFunction(T value, int hashBitLength);

I specialized this for C strings:

template <> UInt32 myHashFunction(const char *str, int hashBitLength);

In most cases, I use a string and get the specialized version, but in a few situations, I get the general implementation instead. I experimented with partial specialization (i.e. ...myHashFunction (const T *pointer... ), but it still goes with the general case. The debugger says that the class from which I call myHashFunction is of type myClass<char const *>, but I believe "const char *" and "char const *" are equivalent in C++. Anyway, I tried every permutation I could think of to no avail.

I have a guess why this might be happening.

[PBG4:~/temp] steve$ cat template.cc
#include <cstdio>
template <typename T> void f( T t ) { puts( "general" ); }
template<> void f<const char *>( const char *s ) { puts( s ); }

int main()
{
        char foo[] = "non const";
        const char *bar = "const";
        f( foo );
        f( bar );
        return 0;
}
[PBG4:~/temp] steve$ g++ -Wall -std=c++98 template.cc
[PBG4:~/temp] steve$ ./a.out
general
const

--
Steve Checkoway

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