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std::erase,std::erase_if(std::forward_list)(3) | C++ Standard Libary | std::erase,std::erase_if(std::forward_list)(3) |
NAME¶
std::erase,std::erase_if(std::forward_list) - std::erase,std::erase_if(std::forward_list)
Synopsis¶
Defined in header <forward_list>
template< class T, class Alloc, class U >
typename std::forward_list<T,Alloc>::size_type (1) (since
C++20)
erase( std::forward_list<T,Alloc>& c, const U& value );
template< class T, class Alloc, class Pred >
typename std::forward_list<T,Alloc>::size_type (2) (since
C++20)
erase_if( std::forward_list<T,Alloc>& c, Pred pred );
1) Erases all elements that compare equal to value from the container.
Equivalent to
return c.remove_if([&](auto& elem) { return elem == value; });
2) Erases all elements that satisfy the predicate pred from the container.
Equivalent to return c.remove_if(pred);
Parameters¶
c - container from which to erase
value - value to be removed
unary predicate which returns true if the element should be erased.
The expression pred(v) must be convertible to bool for every argument v of
pred - type (possibly const) T, regardless of value category, and must not
modify
v. Thus, a parameter type of T&is not allowed
, nor is T unless for T a move is equivalent to a copy
(since C++11).
Return value¶
The number of erased elements.
Complexity¶
Linear.
Notes¶
Unlike std::forward_list::remove, erase accepts heterogenous
types and does not
force a conversion to the container's value type before invoking the ==
operator.
Example¶
// Run this code
#include <iostream>
#include <numeric>
#include <string_view>
#include <forward_list>
void print_container(std::string_view comment, const
std::forward_list<char>& c)
{
std::cout << comment << "{ ";
for (auto x : c) {
std::cout << x << ' ';
}
std::cout << "}\n";
}
int main()
{
std::forward_list<char> cnt(10);
std::iota(cnt.begin(), cnt.end(), '0');
print_container("Initially, cnt = ", cnt);
std::erase(cnt, '3');
print_container("After erase '3', cnt = ", cnt);
auto erased = std::erase_if(cnt, [](char x) { return (x - '0') % 2 == 0; });
print_container("After erase all even numbers, cnt = ", cnt);
std::cout << "Erased even numbers: " << erased <<
'\n';
}
Output:¶
Initially, cnt = { 0 1 2 3 4 5 6 7 8 9 }
After erase '3', cnt = { 0 1 2 4 5 6 7 8 9 }
After erase all even numbers, cnt = { 1 5 7 9 }
Erased even numbers: 5
See also¶
remove removes elements satisfying specific criteria
remove_if (function template)
remove removes elements satisfying specific criteria
remove_if (public member function)
(C++11)
2022.07.31 | http://cppreference.com |