std::not1
From cppreference.com
< cpp | utility | functional
| Defined in header
<functional>
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| template< class Predicate >
std::unary_negate<Predicate> not1(const Predicate& pred); |
(until C++14) | |
| template< class Predicate >
constexpr std::unary_negate<Predicate> not1(const Predicate& pred); |
(since C++14) | |
not1 is a helper function to create a function object that returns the complement of the unary predicate function passed. The function object created is of type std::unary_negate<Predicate>.
The unary predicate type must define a member type, argument_type, that is convertible to the predicate's parameter type. The unary function objects obtained from std::ref, std::cref, std::negate, std::logical_not, std::mem_fn, std::function, std::hash, or from another call to std::not1 have this type defined, as are function objects derived from the deprecated std::unary_function.
Contents |
[edit] Parameters
| pred | - | unary predicate |
[edit] Return value
std::not1 returns an object of type std::unary_negate<Predicate>, constructed with pred.
[edit] Exceptions
None.
[edit] Example
Run this code
#include <algorithm> #include <functional> #include <iostream> #include <vector> struct LessThan7 : std::unary_function<int, bool> { bool operator()(int i) const { return i < 7; } }; int main() { std::vector<int> v; for (int i = 0; i < 10; ++i) { v.push_back(i); } std::cout << std::count_if(v.begin(), v.end(), std::not1(LessThan7())) << "\n"; //same as above, but use a lambda function std::function<int(int)> less_than_9 = [](int x){ return x < 9; }; std::cout << std::count_if(v.begin(), v.end(), std::not1(less_than_9)) << "\n"; }
Output:
3 1
[edit] See also
| wrapper function object returning the complement of the unary predicate it holds (class template) |
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| (C++11)
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wraps callable object of any type with specified function call signature (class template) |
| constructs custom std::binary_negate object (function template) |
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| (deprecated)
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creates an adaptor-compatible function object wrapper from a pointer to function (function template) |
| (deprecated)
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adaptor-compatible unary function base class (class template) |