template template arguments and default parameters

From:
avasilev <alxvasilev@gmail.com>
Newsgroups:
comp.lang.c++
Date:
Thu, 6 Oct 2011 05:19:51 -0700 (PDT)
Message-ID:
<aa448436-df4a-4ec9-9a52-707367da9fdc@x19g2000vbl.googlegroups.com>
HI all,
I have implemented a function that takes a string as input, parses it,
and outputs a map<string, string> of name=value pairs. Something like:

bool parse(const string& input, map<string, string>& output)
However, to make it more flexible, I want to be able to change the
kind of map that is being used, so that it can be a hash_map, multimap
or whatever. For this purpose I need to make the function a template
function. I want as parameter for the template the "map" class name,
and I will use a specialized <string,string>version of it.
I amo ding the following:
template <template <key, value> class T>
bool parse(const string& input, T<string,string> output)
{
....
}

then I try to call the function like this:
std::map<string, string>;
string input = "name=val;name1=val1"
parse<std::map>(input , m);

But this fails to compile, with the error (using gcc):
 error: no matching function for call to
'parse(std::map<std::basic_string<char>, std::basic_string<char> >&,
int)'

I have tried to compile an example where I define the 'map' class, and
it takes strictly two parameters. This compiles fine. It also compiles
if I provide the default template parameters of the std::map class:

template < template < class k, class v, class Compare, class
Allocator> class T >

void parse(const string& input, T < string , string, less<string>,
allocator<pair<const string,string> > > output)

My question is - is there a way to make what I want without providing
all default template parameters, the least reason being that a
different 'map' class may have different default template parameters.

Thanks in advance
Best regards
Alex

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