CODEWITHSUNDEEP
c++templatesmetaprogrammingfunction-templates
zenna
zenna

Reputation: 9176

Template argument deduction (using both explicit and implicit arguments in same call)

I have three template arguments to a function and am having troubles with (I think) the compiler deducing which template argument is which.

The template function is:

#include <structures/partition.h>
#include <vector>

namespace cliques
{
    template <typename P, typename T, typename QF>
    P find_optimal_partition_louvain(cliques::Graph<T> &my_graph,
                                    QF quality_function)
    {

        P dummy;

    }

}

And when I try to call it with

cliques::find_optimal_partition_louvain<cliques::DisjointSetForest>(my_new_graph, cliques::find_linearised_stability(current_markov_time));

Where template argument P should correspond to cliques::DisjointSetForest, and the normal function arguments are a templated class and a function object.

This fails with

error: no matching function for call to
find_optimal_partition_louvain(cliques::Graph<lemon::ListGraph>&,
cliques::find_linearised_stability)

However if I use a builtin type such as an int or a float for the P parameter everything compiles fine.

e.g.

cliques::find_optimal_partition_louvain<int>(my_new_graph, cliques::find_linearised_stability(current_markov_time));

So my question is what am I doing wrong here, how can I use a better inform the compiler which parameter is which, or am I completely off track?

Upvotes: 2

Views: 416

Answers (3)

Mikael Persson
Mikael Persson

Reputation: 18562

I have tried to reproduce the error on a simple example, but I failed to do so (on gcc).

It looks as though the compiler does figure out that find_optimal_partition_louvain is a function template. I suggest trying the following:

cliques::template find_optimal_partition_louvain<cliques::DisjointSetForest>(my_new_graph, cliques::find_linearised_stability(current_markov_time));

Otherwise, you might want to verify if the following simple example compiles fine on your compiler (because it should!):

#include <iostream>

template <class G>
struct Bar { };

namespace Foo {

template <class A, class B, class C>
A some_function(Bar<B>&, C aFunc) {
  aFunc();
  return A();
};

};

struct HWPrinter {
  HWPrinter() { std::cout << "Hello World!" << std::endl; };
};

struct IntPrinter {
  int value;
  IntPrinter(int aValue) : value(aValue) { };
  void operator() () { std::cout << "The integer is: " << value << std::endl; };
};

int main() {
  Bar<HWPrinter> ab;

  Foo::some_function<HWPrinter>(ab,IntPrinter(42));

  return 0;
};

Upvotes: 0

zenna
zenna

Reputation: 9176

I hate to answer my own question but problem was that cliques::DisjointSubsetForest is actually a templated class so 

cliques::find_optimal_partition_louvain<cliques::DisjointSetForest<int> >(my_new_graph, cliques::find_linearised_stability(current_markov_time));

works

Upvotes: 1

Edward Strange
Edward Strange

Reputation: 40859

"error: no matching function for call to ‘find_optimal_partition_louvain(cliques::Graph&, cliques::find_linearised_stability)"

It would seem that your compiler thinks that cliques::Graph is not a template.

Upvotes: 0

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