functors
========

This library contains a set of small but useful functors and functors adapters. See functors_example.cpp for examples.
Minimal gcc : 4.7.2
minimal clang : 3.2

Caution! Extensive usage of c++11 features!

List of utilities:

SkipFunctor 
    takes any number of arguments; does completely nothing

ReturnSomethingFunctor<T,t> 
    takes any number of arguments; returns t;

IdentityFunctor 
    takes one parameter and returns it.

ReturnFalseFunctor
    takes any number of arguments; returns false;
    
ReturnTrueFunctor  
    takes any number of arguments; returns true;

ReturnZeroFunctor 
    takes any number of arguments; returns 0;

AssertFunctor 
    takes any number of arguments; asserts;

ArrayToFunctor<Array>
    Stores an object which provides operator[]. 
    Provides operator()().

A set of non-template comparison functors (only operator() is templated):
  * Greater 
  * Less 
  * GreaterEqual 
  * LessEqual 
  * EqualTo 
  * NotEqualTo 
   

FunctorToComparator<Functor, Compare>
    This comparator  takes a functor "f" and a comparator "c".
    For elements (x,y) it returns c(f(x), f(y))
    c is Less by default

A set of non-template logical operators functors (only operator() is templated):
    * Not 
    * Or 
    * And 

LiftBinaryOperatorFunctor<Operator, FunctorLeft, FunctorRight>
    Functor stores a binary operator "o" and two functors "f" and "g".
    For given arguments args returns o(f(args), g(args)).

Boolean functor adapters. Each of them stores a boolean functor 
and performs an appropriate logical operation in the operator().

    * NotFunctor<Functor>
    * OrFunctor<FunctorLeft, FunctorRight> 
    * AndFunctor<FunctorLeft, FunctorRight>
    * XorFunctor<FunctorLeft, FunctorRight>