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Standard Template Library Programmer's Guide
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unary_negate<AdaptablePredicate>



Categories: functors, adaptors	Component type: type

Description

Unary_negate is a function object adaptor: it is an Adaptable Predicate that represents the logical negation of some other Adaptable Predicate. That is: if f is an object of class unary_negate<AdaptablePredicate>, then there exists an object pred of class AdaptablePredicate such that f(x) always returns the same value as !pred(x). [1] There is rarely any reason to construct a unary_negate directly; it is almost always easier to use the helper function not1.

Example

Finds the first element in a list that does not lie in the range from 1 to 10.

list<int> L;
...
list<int>::iterator in_range = 
     find_if(L.begin(), L.end(),
             not1(compose2(logical_and<bool>(),
                           bind2nd(greater_equal<int>(), 1),
                           bind2nd(less_equal<int>(), 10))));
assert(in_range == L.end() || !(*in_range >= 1 && *in_range <= 10));

Definition

Defined in the standard header functional, and in the nonstandard backward-compatibility header function.h.

Template parameters

Parameter	Description	Default
`AdaptablePredicate`	The type of the function object that this `unary_negate` is the logical negation of.

Model of

Adaptable Predicate

Type requirements

AdaptablePredicate must be a model of Adaptable Predicate.

Public base classes

unary_function<AdaptablePredicate::argument_type, bool>

Members

Member	Where defined	Description
`argument_type`	Adaptable Unary Function	The type of the argument: `AdaptablePredicate::argument_type`
`result_type`	Adaptable Unary Function	The type of the result: `bool`
`bool operator()(argument_type)`	Unary Function	Function call operator.
unary_negate(const AdaptablePredicate& pred)	`unary_negate`	See below.
template <class AdaptablePredicate> unary_negate<AdaptablePredicate> not1(const AdaptablePredicate& pred);	`unary_negate`	See below.

New members

These members are not defined in the Adaptable Predicate requirements, but are specific to unary_negate.

Member	Description
unary_negate(const AdaptablePredicate& pred)	The constructor. Creates a `unary_negate<AdaptablePredicate>` whose underlying predicate is `pred`.
template <class AdaptablePredicate> unary_negate<AdaptablePredicate> not1(const AdaptablePredicate& pred);	If `p` is of type `AdaptablePredicate` then `not1(p)` is equivalent to `unary_negate<AdaptablePredicate>(p)`, but more convenient. This is a global function, not a member function.

Notes

[1] Strictly speaking, unary_negate is redundant. It can be constructed using the function object logical_not and the adaptor unary_compose.