Context

I have a custom comparator that accepts another comparator and applies an additional check:

template <template <typename> class Comparator, typename T>
struct SoftOrder : public std::binary_function<T, T, bool> {
    bool operator()(const T lhs, const T rhs) const {
        return Comparator<T>()(lhs, rhs) && AnotherCheck();
    }
};

I have a second class that takes a comparator, for example:

template <template <typename> class Comparator>
class Processor { ... };

It is easy to instantiate a Processorwith a standard comparator (e.g. std::less) as follows:

Processor<std::less> processor1;
Processor<std::greater> processor2;

However, it is not so easy to create an instance of c SoftOrder, since the compiler correctly complains about the missing argument of the second template:

Processor<SoftOrder<std::less> > processor3; // <-- Fails to compile

Current solutions

Before posting this question, I came up with several solutions.

The first solution is many derived classes

template <typename T>
struct SoftOrderLessThan : public SoftOrder<std::less, T> {};

template <typename T>
struct SoftOrderGreaterThan : public SoftOrder<std::greater, T> {};

The main disadvantage of this solution is the need to create a new structure every time a new option is required, for example:

template <typename T>
struct SoftOrderLessThan : public SoftOrder<std::less, T> {}; // Never used after the next line.
Processor<SoftOrderLessThan> processor3;

-

template <template <typename> class Comparator>
struct BindToSoftOrder {
    template <typename T>
    struct type : public SoftOrder<Comparator, T> {};
};

, :

Processor<BindToSoftOrder<std::less>::type> processor3;

, , , SoftOrder BindToSoftOrder, template<template<template>>>, .

- ++ 11

template <typename T>
using SoftOrderLessThan = SoftOrder<std::less, T>;

, , , , :

template <typename T>
using SoftOrderLessThan = SoftOrder<std::less, T>; // Never used again
Processor<SoftOrderLessThan> processor3;

,

?

Processor<SomeCoolMetaTemplateBind<SoftOrder, std::less>::type> processor3;

, , - Processor<boost::mpl::bind<SoftOrder, std::less> >, .

++ 03, ++ 11.

, , , .