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#### Adapting Functions

If you want to adapt already existing functions or function objects it will become a repetetive task. Therefor the following boilerplate macros are provided to help you adapt already exsiting functions, thus reducing the need to phoenix.modules.bind functions.

##### BOOST_PHOENIX_ADAPT_FUNCTION_NULLARY

###### Description

`BOOST_PHOENIX_ADAPT_FUNCTION_NULLARY` is a macro that can be used to generate all the necessary boilerplate to make an arbitrary nullary function a lazy function.

| Note
These macros generate no global objects. The resulting lazy functions are real functions that create the lazy function expression object

###### Synopsis

    BOOST_PHOENIX_ADAPT_FUNCTION_NULLARY(
        RETURN_TYPE
      , LAZY_FUNCTION
      , FUNCTION
    )

###### Semantics

The above macro generates all necessary code to have a nullary lazy function `LAZY_FUNCTION` which calls the nullary `FUNCTION` that has the return type `RETURN_TYPE`

###### Header

    #include <boost/phoenix/function/adapt_function.hpp>

###### Example

    namespace demo
    {
        int foo()
        {
            return 42;
        }
    }

    BOOST_PHOENIX_ADAPT_FUNCTION_NULLARY(int, foo, demo::foo)

    int main()
    {
        using boost::phoenix::placeholders::_1;

        assert((_1 + foo())(1) == 43);
    }

##### BOOST_PHOENIX_ADAPT_FUNCTION

###### Description

`BOOST_PHOENIX_ADAPT_FUNCTION` is a macro that can be used to generate all the necessary boilerplate to make an arbitrary function a lazy function.

###### Synopsis

    BOOST_PHOENIX_ADAPT_FUNCTION(
        RETURN_TYPE
      , LAZY_FUNCTION
      , FUNCTION
      , FUNCTION_ARITY
    )

###### Semantics

The above macro generates all necessary code to have a lazy function `LAZY_FUNCTION` which calls `FUNCTION` that has the return type `RETURN_TYPE` with `FUNCTION_ARITY` number of arguments.

###### Header

    #include <boost/phoenix/function/adapt_function.hpp>

###### Example

    namespace demo
    {
        int plus(int a, int b)
        {
            return a + b;
        }

        template <typename T>
        T
        plus(T a, T b, T c)
        {
            return a + b + c;
        }
    }

    BOOST_PHOENIX_ADAPT_FUNCTION(int, plus, demo::plus, 2)

    BOOST_PHOENIX_ADAPT_FUNCTION(
        typename remove_reference<A0>::type
      , plus
      , demo::plus
      , 3
    )

    int main()
    {
        using boost::phoenix::arg_names::arg1;
        using boost::phoenix::arg_names::arg2;

        int a = 123;
        int b = 256;

        assert(plus(arg1, arg2)(a, b) == a+b);
        assert(plus(arg1, arg2, 3)(a, b) == a+b+3);
    }

##### BOOST_PHOENIX_ADAPT_CALLABLE_NULLARY

###### Description

`BOOST_PHOENIX_ADAPT_CALLABLE_NULLARY` is a macro that can be used to generate all the necessary boilerplate to make an arbitrary nullary function object a lazy function.

###### Synopsis

    BOOST_PHOENIX_ADAPT_CALLABLE_NULLARY(
        LAZY_FUNCTION
      , CALLABLE
    )

###### Semantics

The above macro generates all necessary code to create `LAZY_FUNCTION` which creates a lazy function object that represents a nullary call to `CALLABLE`. The return type is specified by `CALLABLE` conforming to the Boost.Result Of protocol.

###### Header

    #include <boost/phoenix/function/adapt_callable.hpp>

###### Example

    namespace demo
    {
        struct foo
        {
            typedef int result_type;

            result_type operator()() const
            {
                return 42;
            }
        }
    }

    BOOST_PHOENIX_ADAPT_CALLABLE_NULLARY(foo, demo::foo)

    int main()
    {
        using boost::phoenix::placeholders::_1;

        assert((_1 + foo())(1) == 43);
    }

##### BOOST_PHOENIX_ADAPT_CALLABLE

###### Description

`BOOST_PHOENIX_ADAPT_CALLABLE` is a macro that can be used to generate all the necessary boilerplate to make an arbitrary function object a lazy function.

###### Synopsis

    BOOST_PHOENIX_ADAPT_CALLABLE(
        LAZY_FUNCTION
      , FUNCTION_NAME
      , FUNCTION_ARITY
    )

###### Semantics

The above macro generates all necessary code to create `LAZY_FUNCTION` which creates a lazy function object that represents a call to `CALLABLE` with `FUNCTION_ARITY` arguments. The return type is specified by `CALLABLE` conforming to the Boost.Result Of protocol.

###### Header

    #include <boost/phoenix/function/adapt_callable.hpp>

###### Example

    namespace demo
    {
        struct plus
        {
            template <typename Sig>
            struct result;

            template <typename This, typename A0, typename A1>
            struct result<This(A0, A1)>
                : remove_reference<A0>
            {};

            template <typename This, typename A0, typename A1, typename A2>
            struct result<This(A0, A1, A2)>
                : remove_reference<A0>
            {};

            template <typename A0, typename A1>
            A0 operator()(A0 const & a0, A1 const & a1) const
            {
                return a0 + a1;
            }

            template <typename A0, typename A1, typename A2>
            A0 operator()(A0 const & a0, A1 const & a1, A2 const & a2) const
            {
                return a0 + a1 + a2;
            }
        };
    }

    BOOST_PHOENIX_ADAPT_CALLABLE(plus, demo::plus, 2)

    BOOST_PHOENIX_ADAPT_CALLABLE(plus, demo::plus, 3)

    int main()
    {
        using boost::phoenix::arg_names::arg1;
        using boost::phoenix::arg_names::arg2;

        int a = 123;
        int b = 256;

        assert(plus(arg1, arg2)(a, b) == a+b);
        assert(plus(arg1, arg2, 3)(a, b) == a+b+3);
    }