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Categories: functors, adaptors Component type: type


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.


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(),
                           bind2nd(greater_equal<int>(), 1),
                           bind2nd(less_equal<int>(), 10))));
assert(in_range == L.end() || !(*in_range >= 1 && *in_range <= 10));


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>


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>
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>
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.


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

See also

The function object overview, Adaptable Predicate, Predicate, binary_negate, unary_compose, binary_compose

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