.\" ident @(#)Negators.3
.\" Standard Template Library
.\" $$RW_INSERT_HEADER "slyrs.man"
.TH Negators 3C++ "02 Apr 1998" "Rogue Wave Software" "-"
.ce2
Standard C++ Library   
Copyright 1998, Rogue Wave Software, Inc.   

.SH NAME

\f2Negators\fP

\ - Function adaptors and function objects used to reverse the sense of predicate function objects.



.SH  SYNOPSIS


.br
#include <functional>
.br
template <class Predicate>
.br
class unary_negate;
.br

.br
template <class Predicate>
.br
unary_negate<Predicate> not1(const Predicate&);
.br

.br
template <class Predicate>
.br
class binary_negate;
.br

.br
template <class Predicate>
.br
binary_negate<Predicate> not2(const Predicate&);



.SH  DESCRIPTION


Negators not1 and not2 are functions that take predicate function objects as arguments and return predicate function objects with the opposite sense. Negators work only with function objects defined as subclasses of the classes unary_function and binary_function. not1 accepts and returns unary predicate function objects. not2 accepts and returns binary predicate function objects.

unary_negate and binary_negate are function object classes that include return types for the negators, not1 and not2.



.SH  INTERFACE


.br
template <class Predicate>
.br
class unary_negate
.RE
.RS 2
: public unary_function
.RE
.RS 11
<typename Predicate::argument_type, bool> {
.RE
.RS 0

.br
public:
.RE
.RS 1
explicit unary_negate (const Predicate&);
.br
bool operator() (const argument_type&) const;
.RE
.RS 0
};
.br

.br
template<class Predicate>
.br
unary_negate <Predicate> not1 (const Predicate&);
.br

.br
template<class Predicate>
.br
class binary_negate
.RE
.RS 2
: public binary_function
.RE
.RS 11
<typename Predicate::first_argument_type,
.br
typename Predicate::second_argument_type, bool>
.RE
.RS 0
{
.br
public:
.RE
.RS 1
explicit binary_negate (const Predicate&);
.br
bool operator() (const first_argument_type&,
.RE
.RS 18
const second_argument_type&) const;
.RE
.RS 0
};
.br

.br
template <class Predicate>
.br
binary_negate<Predicate> not2 (const Predicate&);



.SH  EXAMPLE



.br
//
.br
// negator.cpp
.br
//
.RE
.RS 1
#include<functional>
.br
#include<algorithm>
.br
#include <iostream>
.RE
.RS 0
using namespace std;
.br

.RE
.RS 1
//Create a new predicate from unary_function
.RE
.RS 0
template<class Arg>
.br
class is_odd : public unary_function<Arg, bool>
.RE
.RS 1
{
.RE
.RS 2
public:
.br
bool operator()(const Arg& arg1) const
.RE
.RS 3
{
.RE
.RS 4
return (arg1 % 2 ? true : false);
.RE
.RS 3
}
.RE
.RS 1
};
.RE
.RS 0

.br
int main()
.RE
.RS 1
{
.RE
.RS 2
less<int> less_func;
.RE
.RS 0

.RE
.RS 3
// Use not2 on less
.RE
.RS 2
cout << (less_func(1,4) ? "TRUE" : "FALSE") << endl;
.br
cout << (less_func(4,1) ? "TRUE" : "FALSE") << endl;
.br
cout << (not2(less<int>())(1,4) ? "TRUE" : "FALSE") 
.RE
.RS 8
<< endl;
.RE
.RS 2
cout << (not2(less<int>())(4,1) ? "TRUE" : "FALSE") 
.RE
.RS 8
<< endl;   
.RE
.RS 0

.RE
.RS 3
//Create an instance of our predicate
.RE
.RS 2
is_odd<int> odd;
.RE
.RS 0

.RE
.RS 3
// Use not1 on our user defined predicate
.RE
.RS 2
cout << (odd(1) ? "TRUE" : "FALSE") << endl;
.br
cout << (odd(4) ? "TRUE" : "FALSE") << endl;
.br
cout << (not1(odd)(1) ? "TRUE" : "FALSE") << endl;
.br
cout << (not1(odd)(4) ? "TRUE" : "FALSE") << endl;
.RE
.RS 0

.RE
.RS 2
return 0;
.RE
.RS 1
}

.br
.RE
.RS 0
Program Output



.RE
.RS 0

.br
TRUE
.br
FALSE
.br
FALSE
.br
TRUE
.br
TRUE
.br
FALSE
.br
FALSE
.br
TRUE



.SH  SEE ALSO


Algorithms, binary_function, Function_Objects, unary_function