compose.hpp

The following code example is taken from the book
The C++ Standard Library - A Tutorial and Reference
by Nicolai M. Josuttis, Addison-Wesley, 1999
© Copyright Nicolai M. Josuttis 1999
`/* supplementing compose function objects
* Son Dez 26 22:11:12 MET 1999
*/
#ifndef BOOST_COMPOSE_HPP
#define BOOST_COMPOSE_HPP
#include <functional>
namespace boost {
/**********************************************************
* type nullary_function
* - as supplement to unary_function and binary_function
**********************************************************/
template <class Result>
struct nullary_function {
typedef Result result_type;
};
/**********************************************************
* ptr_fun for functions with no argument
**********************************************************/
template <class Result>
class pointer_to_nullary_function : public nullary_function<Result>
{
protected:
Result (*ptr)();
public:
pointer_to_nullary_function() {
}
explicit pointer_to_nullary_function(Result (*x)()) : ptr(x) {
}
Result operator()() const {
return ptr();
}
};
template <class Result>
inline pointer_to_nullary_function<Result> ptr_fun(Result (*x)())
{
return pointer_to_nullary_function<Result>(x);
}
/*********** compose_f_gx_t and compose_f_gx **********************/
/* class for the compose_f_gx adapter
*/
template <class OP1, class OP2>
class compose_f_gx_t
: public std::unary_function<typename OP2::argument_type,
typename OP1::result_type>
{
private:
OP1 op1; // process: op1(op2(x))
OP2 op2;
public:
// constructor
compose_f_gx_t(const OP1& o1, const OP2& o2)
: op1(o1), op2(o2) {
}
// function call
typename OP1::result_type
operator()(const typename OP2::argument_type& x) const {
return op1(op2(x));
}
};
/* convenience functions for the compose_f_gx adapter
*/
template <class OP1, class OP2>
inline compose_f_gx_t<OP1,OP2>
compose_f_gx (const OP1& o1, const OP2& o2) {
return compose_f_gx_t<OP1,OP2>(o1,o2);
}
/*********** compose_f_gx_hx_t and compose_f_gx_hx **********************/
/* class for the compose_f_gx_hx adapter
*/
template <class OP1, class OP2, class OP3>
class compose_f_gx_hx_t
: public std::unary_function<typename OP2::argument_type,
typename OP1::result_type>
{
private:
OP1 op1; // process: op1(op2(x),op3(x))
OP2 op2;
OP3 op3;
public:
// constructor
compose_f_gx_hx_t (const OP1& o1, const OP2& o2, const OP3& o3)
: op1(o1), op2(o2), op3(o3) {
}
// function call
typename OP1::result_type
operator()(const typename OP2::argument_type& x) const {
return op1(op2(x),op3(x));
}
};
/* convenience functions for the compose_f_gx_hx adapter
*/
template <class OP1, class OP2, class OP3>
inline compose_f_gx_hx_t<OP1,OP2,OP3>
compose_f_gx_hx (const OP1& o1, const OP2& o2, const OP3& o3) {
return compose_f_gx_hx_t<OP1,OP2,OP3>(o1,o2,o3);
}
/*********** compose_f_gxy_t and compose_f_gxy **********************/
/* class for the compose_f_gxy adapter
*/
template <class OP1, class OP2>
class compose_f_gxy_t
: public std::binary_function<typename OP2::first_argument_type,
typename OP2::second_argument_type,
typename OP1::result_type>
{
private:
OP1 op1; // process: op1(op2(x,y))
OP2 op2;
public:
// constructor
compose_f_gxy_t (const OP1& o1, const OP2& o2)
: op1(o1), op2(o2) {
}
// function call
typename OP1::result_type
operator()(const typename OP2::first_argument_type& x,
const typename OP2::second_argument_type& y) const {
return op1(op2(x,y));
}
};
/* convenience function for the compose_f_gxy adapter
*/
template <class OP1, class OP2>
inline compose_f_gxy_t<OP1,OP2>
compose_f_gxy (const OP1& o1, const OP2& o2) {
return compose_f_gxy_t<OP1,OP2>(o1,o2);
}
/*********** compose_f_gx_hy_t and compose_f_gx_hy **********************/
/* class for the compose_f_gx_hy adapter
*/
template <class OP1, class OP2, class OP3>
class compose_f_gx_hy_t
: public std::binary_function<typename OP2::argument_type,
typename OP3::argument_type,
typename OP1::result_type>
{
private:
OP1 op1; // process: op1(op2(x),op3(y))
OP2 op2;
OP3 op3;
public:
// constructor
compose_f_gx_hy_t (const OP1& o1, const OP2& o2, const OP3& o3)
: op1(o1), op2(o2), op3(o3) {
}
// function call
typename OP1::result_type
operator()(const typename OP2::argument_type& x,
const typename OP3::argument_type& y) const {
return op1(op2(x),op3(y));
}
};
/* convenience function for the compose_f_gx_hy adapter
*/
template <class OP1, class OP2, class OP3>
inline compose_f_gx_hy_t<OP1,OP2,OP3>
compose_f_gx_hy (const OP1& o1, const OP2& o2, const OP3& o3) {
return compose_f_gx_hy_t<OP1,OP2,OP3>(o1,o2,o3);
}
/*********** compose_f_g_t and compose_f_g **********************/
/* class for the compose_f_g adapter
*/
template <class OP1, class OP2>
class compose_f_g_t
: public boost::nullary_function<typename OP1::result_type>
{
private:
OP1 op1; // process: op1(op2())
OP2 op2;
public:
// constructor
compose_f_g_t(const OP1& o1, const OP2& o2)
: op1(o1), op2(o2) {
}
// function call
typename OP1::result_type
operator()() const {
return op1(op2());
}
};
/* convenience functions for the compose_f_g adapter
*/
template <class OP1, class OP2>
inline compose_f_g_t<OP1,OP2>
compose_f_g (const OP1& o1, const OP2& o2) {
return compose_f_g_t<OP1,OP2>(o1,o2);
}
} /* namespace boost */
#endif /*BOOST_COMPOSE_HPP*/
/* supplementing compose function objects
* Son Dez 26 22:14:55 MET 1999
*/
#ifndef BOOST_COMPOSE_HPP
#define BOOST_COMPOSE_HPP
#include <functional>
namespace boost {
/**********************************************************
* type nullary_function
* - as supplement to unary_function and binary_function
**********************************************************/
template <class Result>
struct nullary_function {
typedef Result result_type;
};
/**********************************************************
* ptr_fun for functions with no argument
**********************************************************/
template <class Result>
class pointer_to_nullary_function : public nullary_function<Result>
{
protected:
Result (*ptr)();
public:
pointer_to_nullary_function() {
}
explicit pointer_to_nullary_function(Result (*x)()) : ptr(x) {
}
Result operator()() const {
return ptr();
}
};
template <class Result>
inline pointer_to_nullary_function<Result> ptr_fun(Result (*x)())
{
return pointer_to_nullary_function<Result>(x);
}
/*********** compose_f_gx_t and compose_f_gx **********************/
/* class for the compose_f_gx adapter
*/
template <class OP1, class OP2>
class compose_f_gx_t
: public std::unary_function<typename OP2::argument_type,
typename OP1::result_type>
{
private:
OP1 op1; // process: op1(op2(x))
OP2 op2;
public:
// constructor
compose_f_gx_t(const OP1& o1, const OP2& o2)
: op1(o1), op2(o2) {
}
// function call
typename OP1::result_type
operator()(const typename OP2::argument_type& x) const {
return op1(op2(x));
}
};
/* convenience functions for the compose_f_gx adapter
*/
template <class OP1, class OP2>
inline compose_f_gx_t<OP1,OP2>
compose_f_gx (const OP1& o1, const OP2& o2) {
return compose_f_gx_t<OP1,OP2>(o1,o2);
}
/*********** compose_f_gx_hx_t and compose_f_gx_hx **********************/
/* class for the compose_f_gx_hx adapter
*/
template <class OP1, class OP2, class OP3>
class compose_f_gx_hx_t
: public std::unary_function<typename OP2::argument_type,
typename OP1::result_type>
{
private:
OP1 op1; // process: op1(op2(x),op3(x))
OP2 op2;
OP3 op3;
public:
// constructor
compose_f_gx_hx_t (const OP1& o1, const OP2& o2, const OP3& o3)
: op1(o1), op2(o2), op3(o3) {
}
// function call
typename OP1::result_type
operator()(const typename OP2::argument_type& x) const {
return op1(op2(x),op3(x));
}
};
/* convenience functions for the compose_f_gx_hx adapter
*/
template <class OP1, class OP2, class OP3>
inline compose_f_gx_hx_t<OP1,OP2,OP3>
compose_f_gx_hx (const OP1& o1, const OP2& o2, const OP3& o3) {
return compose_f_gx_hx_t<OP1,OP2,OP3>(o1,o2,o3);
}
/*********** compose_f_gxy_t and compose_f_gxy **********************/
/* class for the compose_f_gxy adapter
*/
template <class OP1, class OP2>
class compose_f_gxy_t
: public std::binary_function<typename OP2::first_argument_type,
typename OP2::second_argument_type,
typename OP1::result_type>
{
private:
OP1 op1; // process: op1(op2(x,y))
OP2 op2;
public:
// constructor
compose_f_gxy_t (const OP1& o1, const OP2& o2)
: op1(o1), op2(o2) {
}
// function call
typename OP1::result_type
operator()(const typename OP2::first_argument_type& x,
const typename OP2::second_argument_type& y) const {
return op1(op2(x,y));
}
};
/* convenience function for the compose_f_gxy adapter
*/
template <class OP1, class OP2>
inline compose_f_gxy_t<OP1,OP2>
compose_f_gxy (const OP1& o1, const OP2& o2) {
return compose_f_gxy_t<OP1,OP2>(o1,o2);
}
/*********** compose_f_gx_hy_t and compose_f_gx_hy **********************/
/* class for the compose_f_gx_hy adapter
*/
template <class OP1, class OP2, class OP3>
class compose_f_gx_hy_t
: public std::binary_function<typename OP2::argument_type,
typename OP3::argument_type,
typename OP1::result_type>
{
private:
OP1 op1; // process: op1(op2(x),op3(y))
OP2 op2;
OP3 op3;
public:
// constructor
compose_f_gx_hy_t (const OP1& o1, const OP2& o2, const OP3& o3)
: op1(o1), op2(o2), op3(o3) {
}
// function call
typename OP1::result_type
operator()(const typename OP2::argument_type& x,
const typename OP3::argument_type& y) const {
return op1(op2(x),op3(y));
}
};
/* convenience function for the compose_f_gx_hy adapter
*/
template <class OP1, class OP2, class OP3>
inline compose_f_gx_hy_t<OP1,OP2,OP3>
compose_f_gx_hy (const OP1& o1, const OP2& o2, const OP3& o3) {
return compose_f_gx_hy_t<OP1,OP2,OP3>(o1,o2,o3);
}
/*********** compose_f_g_t and compose_f_g **********************/
/* class for the compose_f_g adapter
*/
template <class OP1, class OP2>
class compose_f_g_t
: public boost::nullary_function<typename OP1::result_type>
{
private:
OP1 op1; // process: op1(op2())
OP2 op2;
public:
// constructor
compose_f_g_t(const OP1& o1, const OP2& o2)
: op1(o1), op2(o2) {
}
// function call
typename OP1::result_type
operator()() const {
return op1(op2());
}
};
/* convenience functions for the compose_f_g adapter
*/
template <class OP1, class OP2>
inline compose_f_g_t<OP1,OP2>
compose_f_g (const OP1& o1, const OP2& o2) {
return compose_f_g_t<OP1,OP2>(o1,o2);
}
} /* namespace boost */
#endif /*BOOST_COMPOSE_HPP*/
`