<functional>

binary_function · binary_negate · binder1st · binder2nd · const_mem_fun_t · const_mem_fun_ref_t · const_mem_fun1_t · const_mem_fun1_ref_t · divides · equal_to · greater · greater_equal · less · less_equal · logical_and · logical_not · logical_or · mem_fun_t · mem_fun_ref_t · mem_fun1_t · mem_fun1_ref_t · minus · modulus · multiplies · negate · not_equal_to · plus · pointer_to_binary_function · pointer_to_unary_function · unary_function · unary_negate

bind1st · bind2nd · mem_fun · mem_fun_ref · not1 · not2 · ptr_fun

Include the STL standard header <functional> to define several templates that help construct function objects, objects of a type that defines operator(). A function object can thus be a function pointer, but in the more general case the object can store additional information that can be used during a function call.

namespace std {
template<class Arg, class Result>
    struct unary_function;
template<class Arg1, class Arg2, class Result>
    struct binary_function;
template<class Ty>
    struct plus;
template<class Ty>
    struct minus;
template<class Ty>
    struct multiplies;
template<class Ty>
    struct divides;
template<class Ty>
    struct modulus;
template<class Ty>
    struct negate;
template<class Ty>
    struct equal_to;
template<class Ty>
    struct not_equal_to;
template<class Ty>
    struct greater;
template<class Ty>
    struct less;
template<class Ty>
    struct greater_equal;
template<class Ty>
    struct less_equal;
template<class Ty>
    struct logical_and;
template<class Ty>
    struct logical_or;
template<class Ty>
    struct logical_not;
template<class Fn1>
    struct unary_negate;
template<class Fn2>
    struct binary_negate;
template<class Fn2>
    class binder1st;
template<class Fn2>
    class binder2nd;
template<class Arg, class Result>
    class pointer_to_unary_function;
template<class Arg1, class Arg2, class Result>
    class pointer_to_binary_function;
template<class Result, class Ty>
    struct mem_fun_t;
template<class Result, class Ty, class Arg>
    struct mem_fun1_t;
template<class Result, class Ty>
    struct const_mem_fun_t;
template<class Result, class Ty, class Arg>
    struct const_mem_fun1_t;
template<class Result, class Ty>
    struct mem_fun_ref_t;
template<class Result, class Ty, class Arg>
    struct mem_fun1_ref_t;
template<class Result, class Ty>
    struct const_mem_fun_ref_t;
template<class Result, class Ty, class Arg>
    struct const_mem_fun1_ref_t;

        // TEMPLATE FUNCTIONS
template<class Fn1>
    unary_negate<Fn1> not1(const Fn1& func);
template<class Fn2>
    binary_negate<Fn2> not2(const Fn2& func);
template<class Fn2, class Ty>
    binder1st<Fn2> bind1st(const Fn2& func, const Ty& left);
template<class Fn2, class Ty>
    binder2nd<Fn2> bind2nd(const Fn2& func, const Ty& right);
template<class Arg, class Result>
    pointer_to_unary_function<Arg, Result>
        ptr_fun(Result (*)(Arg));
template<class Arg1, class Arg2, class Result>
    pointer_to_binary_function<Arg1, Arg2, Result>
        ptr_fun(Result (*)(Arg1, Arg2));
template<class Result, class Ty>
    mem_fun_t<Result, Ty> mem_fun(Result (Ty::*pm)());
template<class Result, class Ty, class Arg>
    mem_fun1_t<Result, Ty, Arg> mem_fun(Result (Ty::*pm)(Arg left));
template<class Result, class Ty>
    const_mem_fun_t<Result, Ty> mem_fun(Result (Ty::*pm)() const);
template<class Result, class Ty, class Arg>
    const_mem_fun1_t<Result, Ty, Arg> mem_fun(Result (Ty::*pm)(Arg left) const);
template<class Result, class Ty>
    mem_fun_ref_t<Result, Ty> mem_fun_ref(Result (Ty::*pm)());
template<class Result, class Ty, class Arg>
    mem_fun1_ref_t<Result, Ty, Arg>
        mem_fun_ref(Result (Ty::*pm)(Arg left));
template<class Result, class Ty>
    const_mem_fun_ref_t<Result, Ty> mem_fun_ref(Result (Ty::*pm)() const);
template<class Result, class Ty, class Arg>
    const_mem_fun1_ref_t<Result, Ty, Arg>
        mem_fun_ref(Result (Ty::*pm)(Arg left) const);
}  // namespace std

binary_function

template<class Arg1, class Arg2, class Result>
    struct binary_function {
    typedef Arg1 first_argument_type;
    typedef Arg2 second_argument_type;
    typedef Result result_type;
    };

The template class serves as a base for classes that define a member function of the form:

result_type operator()(const first_argument_type&,
    const second_argument_type&) const

or a similar form taking two arguments.

Hence, all such binary functions can refer to their first argument type as first_argument_type, their second argument type as second_argument_type, and their return type as result_type.

binary_negate

template<class Fn2>
    class binary_negate
        : public binary_function<
            typename Fn2::first_argument_type,
            typename Fn2::second_argument_type, bool> {
public:
    explicit binary_negate(const Fn2& func);
    bool operator()(
        const typename Fn2::first_argument_type& left,
        const typename Fn2::second_argument_type& right) const;
    };

The template class stores a copy of func, which must be a binary function object. It defines its member function operator() as returning !func(left, right).

bind1st

template<class Fn2, class Ty>
    binder1st<Fn2> bind1st(const Fn2& func, const Ty& left);

The function returns binder1st<Fn2>(func, typename Fn2::first_argument_type(left)).

bind2nd

template<class Fn2, class Ty>
    binder2nd<Fn2> bind2nd(const Fn2& func, const Ty& right);

The function returns binder2nd<Fn2>(func, typename Fn2::second_argument_type(right)).

binder1st

template<class Fn2>
    class binder1st
        : public unary_function<
            typename Fn2::second_argument_type,
            typename Fn2::result_type> {
public:
    typedef typename Fn2::second_argument_type argument_type;
    typedef typename Fn2::result_type result_type;
    binder1st(const Fn2& func,
        const typename Fn2::first_argument_type& left);
    result_type operator()(const argument_type& right) const;
protected:
    Fn2 op;
    typename Fn2::first_argument_type value;
    };

The template class stores a copy of func, which must be a binary function object, in op, and a copy of left in value. It defines its member function operator() as returning op(value, right).

binder2nd

template<class Fn2>
    class binder2nd
        : public unary_function<
            typename Fn2::first_argument_type,
            typename Fn2::result_type> {
public:
    typedef typename Fn2::first_argument_type argument_type;
    typedef typename Fn2::result_type result_type;
    binder2nd(const Fn2& func,
        const typename Fn2::second_argument_type& right);
    result_type operator()(const argument_type& left) const;
protected:
    Fn2 op;
    typename Fn2::second_argument_type value;
    };

The template class stores a copy of func, which must be a binary function object, in op, and a copy of right in value. It defines its member function operator() as returning op(left, value).

const_mem_fun_t

template<class Result, class Ty>
    struct const_mem_fun_t
        : public unary_function<const Ty *, Result> {
    explicit const_mem_fun_t(Result (Ty::*pm)() const);
    Result operator()(const Ty *pleft) const;
    };

The template class stores a copy of pm, which must be a pointer to a member function of class Ty, in a private member object. It defines its member function operator() as returning (pleft->*pm)() const.

const_mem_fun_ref_t

template<class Result, class Ty>
    struct const_mem_fun_ref_t
        : public unary_function<Ty, Result> {
    explicit const_mem_fun_t(Result (Ty::*pm)() const);
    Result operator()(const Ty& left) const;
    };

The template class stores a copy of pm, which must be a pointer to a member function of class Ty, in a private member object. It defines its member function operator() as returning (left.*pm)() const.

const_mem_fun1_t

template<class Result, class Ty, class Arg>
    struct const_mem_fun1_t
        : public binary_function<const Ty *, Arg, Result> {
    explicit const_mem_fun1_t(Result (Ty::*pm)(Arg) const);
    Result operator()(const Ty *pleft, Arg right) const;
    };

The template class stores a copy of pm, which must be a pointer to a member function of class Ty, in a private member object. It defines its member function operator() as returning (pleft->*pm)(right) const.

const_mem_fun1_ref_t

template<class Result, class Ty, class Arg>
    struct const_mem_fun1_ref_t
        : public binary_function<Ty, Arg, Result> {
    explicit const_mem_fun1_ref_t(Result (Ty::*pm)(Arg) const);
    Result operator()(const Ty& left, Arg right) const;
    };

The template class stores a copy of pm, which must be a pointer to a member function of class Ty, in a private member object. It defines its member function operator() as returning (left.*pm)(right) const.

divides

template<class Ty>
    struct divides : public binary_function<Ty, Ty, Ty> {
    Ty operator()(const Ty& left, const Ty& right) const;
    };

The template class defines its member function as returning left / right.

equal_to

template<class Ty>
    struct equal_to
        : public binary_function<Ty, Ty, bool> {
    bool operator()(const Ty& left, const Ty& right) const;
    };

The template class defines its member function as returning left == right.

greater

template<class Ty>
    struct greater : public binary_function<Ty, Ty, bool> {
    bool operator()(const Ty& left, const Ty& right) const;
    };

The template class defines its member function as returning left > right. The member function defines a total ordering if Ty is an object pointer type. (It will compare two pointer values consistently even if they don't point into the same array.)

greater_equal

template<class Ty>
    struct greater_equal
        : public binary_function<Ty, Ty, bool> {
    bool operator()(const Ty& left, const Ty& right) const;
    };

The template class defines its member function as returning left >= right. The member function defines a total ordering if Ty is an object pointer type. (It will compare two pointer values consistently even if they don't point into the same array.)

less

template<class Ty>
    struct less : public binary_function<Ty, Ty, bool> {
    bool operator()(const Ty& left, const Ty& right) const;
    };

The template class defines its member function as returning left < right. The member function defines a total ordering if Ty is an object pointer type. (It will compare two pointer values consistently even if they don't point into the same array.)

less_equal

template<class Ty>
    struct less_equal
        : public binary_function<Ty, Ty, bool> {
    bool operator()(const Ty& left, const Ty& right) const;
    };

The template class defines its member function as returning left <= right. The member function defines a total ordering if Ty is an object pointer type. (It will compare two pointer values consistently even if they don't point into the same array.)

logical_and

template<class Ty>
    struct logical_and
        : public binary_function<Ty, Ty, bool> {
    bool operator()(const Ty& left, const Ty& right) const;
    };

The template class defines its member function as returning left && right.

logical_not

template<class Ty>
    struct logical_not : public unary_function<Ty, bool> {
    bool operator()(const Ty& left) const;
    };

The template class defines its member function as returning !left.

logical_or

template<class Ty>
    struct logical_or
        : public binary_function<Ty, Ty, bool> {
    bool operator()(const Ty& left, const Ty& right) const;
    };

The template class defines its member function as returning left || right.

mem_fun

template<class Result, class Ty>
    mem_fun_t<Result, Ty> mem_fun(Result (Ty::*pm)());
template<class Result, class Ty, class Arg>
    mem_fun1_t<Result, Ty, Arg> mem_fun(Result (Ty::*pm)(Arg));
template<class Result, class Ty>
    const_mem_fun_t<Result, Ty>
        mem_fun(Result (Ty::*pm)() const);
template<class Result, class Ty, class Arg>
    const_mem_fun1_t<Result, Ty, Arg>
        mem_fun(Result (Ty::*pm)(Arg) const);

The template function returns pm cast to the return type.

mem_fun_ref

template<class Result, class Ty>
    mem_fun_ref_t<Result, Ty> mem_fun_ref(Result (Ty::*pm)());
template<class Result, class Ty, class Arg>
    mem_fun1_ref_t<Result, Ty, Arg> mem_fun_ref(Result (Ty::*pm)(Arg));
template<class Result, class Ty>
    const_mem_fun_ref_t<Result, Ty> mem_fun_ref(Result (Ty::*pm)() const);
template<class Result, class Ty, class Arg>
    const_mem_fun1_ref_t<Result, Ty, Arg> mem_fun_ref(Result (Ty::*pm)(Arg) const);

The template function returns pm cast to the return type.

mem_fun_t

template<class Result, class Ty>
    struct mem_fun_t : public unary_function<Ty *, Result> {
    explicit mem_fun_t(Result (Ty::*pm)());
    Result operator()(Ty *pleft) const;
    };

The template class stores a copy of pm, which must be a pointer to a member function of class Ty, in a private member object. It defines its member function operator() as returning (pleft->*pm)().

mem_fun_ref_t

template<class Result, class Ty>
    struct mem_fun_ref_t
        : public unary_function<Ty, Result> {
    explicit mem_fun_t(Result (Ty::*pm)());
    Result operator()(Ty& left) const;
    };

The template class stores a copy of pm, which must be a pointer to a member function of class Ty, in a private member object. It defines its member function operator() as returning (left.*pm)().

mem_fun1_t

template<class Result, class Ty, class Arg>
    struct mem_fun1_t
        : public binary_function<Ty *, Arg, Result> {
    explicit mem_fun1_t(Result (Ty::*pm)(Arg));
    Result operator()(Ty *pleft, Arg right) const;
    };

The template class stores a copy of pm, which must be a pointer to a member function of class Ty, in a private member object. It defines its member function operator() as returning (pleft->*pm)(right).

mem_fun1_ref_t

template<class Result, class Ty, class Arg>
    struct mem_fun1_ref_t
        : public binary_function<Ty, Arg, Result> {
    explicit mem_fun1_ref_t(Result (Ty::*pm)(Arg));
    Result operator()(Ty& left, Arg right) const;
    };

The template class stores a copy of pm, which must be a pointer to a member function of class Ty, in a private member object. It defines its member function operator() as returning (left.*pm)(right).

minus

template<class Ty>
    struct minus : public binary_function<Ty, Ty, Ty> {
    Ty operator()(const Ty& left, const Ty& right) const;
    };

The template class defines its member function as returning left - right.

modulus

template<class Ty>
    struct modulus : public binary_function<Ty, Ty, Ty> {
    Ty operator()(const Ty& left, const Ty& right) const;
    };

The template class defines its member function as returning left % right.

multiplies

template<class Ty>
    struct multiplies : public binary_function<Ty, Ty, Ty> {
    Ty operator()(const Ty& left, const Ty& right) const;
    };

The template class defines its member function as returning left * right.

negate

template<class Ty>
    struct negate : public unary_function<Ty, Ty> {
    Ty operator()(const Ty& left) const;
    };

The template class defines its member function as returning -left.

not1

template<class Fn1>
    unary_negate<Fn1> not1(const Fn1& func);

The template function returns unary_negate<Fn1>(func).

not2

template<class Fn2>
    binary_negate<Fn2> not2(const Fn2& func);

The template function returns binary_negate<Fn2>(func).

not_equal_to

template<class Ty>
    struct not_equal_to
        : public binary_function<Ty, Ty, bool> {
    bool operator()(const Ty& left, const Ty& right) const;
    };

The template class defines its member function as returning left != right.

plus

template<class Ty>
    struct plus : public binary_function<Ty, Ty, Ty> {
    Ty operator()(const Ty& left, const Ty& right) const;
    };

The template class defines its member function as returning left + right.

pointer_to_binary_function

template<class Arg1, class Arg2, class Result>
    class pointer_to_binary_function
        : public binary_function<Arg1, Arg2, Result> {
public:
    explicit pointer_to_binary_function(
        Result (*pfunc)(Arg1, Arg2));
    Result operator()(const Arg1 left, const Arg2 right) const;
    };

The template class stores a copy of pfunc. It defines its member function operator() as returning (*pfunc)(left, right).

pointer_to_unary_function

template<class Arg, class Result>
    class pointer_to_unary_function
        : public unary_function<Arg, Result> {
public:
    explicit pointer_to_unary_function(
        Result (*pfunc)(Arg));
    Result operator()(const Arg left) const;
    };

The template class stores a copy of pfunc. It defines its member function operator() as returning (*pfunc)(left).

ptr_fun

template<class Arg, class Result>
    pointer_to_unary_function<Arg, Result>
        ptr_fun(Result (*pfunc)(Arg));
template<class Arg1, class Arg2, class Result>
    pointer_to_binary_function<Arg1, Arg2, Result>
        ptr_fun(Result (*pfunc)(Arg1, Arg2));

The first template function returns pointer_to_unary_function<Arg, Result>(pfunc).

The second template function returns pointer_to_binary_function<Arg1, Arg2, Result>(pfunc).

unary_function

template<class Arg, class Result>
    struct unary_function {
    typedef Arg argument_type;
    typedef Result result_type;
    };

The template class serves as a base for classes that define a member function of the form:

result_type operator()(const argument_type&) const

or a similar form taking one argument.

Hence, all such unary functions can refer to their sole argument type as argument_type and their return type as result_type.

unary_negate

template<class Fn1>
    class unary_negate
        : public unary_function<
            typename Fn1::argument_type,
            bool> {
public:
    explicit unary_negate(const Fn1& Func);
    bool operator()(
        const typename Fn1::argument_type& left) const;
    };

The template class stores a copy of func, which must be a unary function object. It defines its member function operator() as returning !func(left).

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Copyright © 1992-2006 by P.J. Plauger. Portions derived from work copyright © 1994 by Hewlett-Packard Company. All rights reserved.