Difference between revisions of "Template:cpp/container/erase2"
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m (→Example: rm hack-implementation of erase/erase_if for inplace_vector.) |
m (`= T` for inplace_vector: P2248R14, it also already present in N4988 (C++26 draft); +demo for `U = T`.) |
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| (3 intermediate revisions by one user not shown) | |||
| Line 11: | Line 11: | ||
|inplace_vector= | |inplace_vector= | ||
{{dcl|num=1|since=c++26|1= | {{dcl|num=1|since=c++26|1= | ||
| − | template< class T, std::size_t N, class U | + | template< class T, std::size_t N, class U = T > |
| − | constexpr typename std::inplace_vector<T, N>::size_type | + | constexpr typename std::inplace_vector<T, N>::size_type |
erase( std::inplace_vector<T, N>& c, const U& value ); | erase( std::inplace_vector<T, N>& c, const U& value ); | ||
}} | }} | ||
{{dcl|num=2|since=c++26| | {{dcl|num=2|since=c++26| | ||
template< class T, std::size_t N, class Pred > | template< class T, std::size_t N, class Pred > | ||
| − | constexpr typename std::inplace_vector<T, N>::size_type | + | constexpr typename std::inplace_vector<T, N>::size_type |
erase_if( std::inplace_vector<T, N>& c, Pred pred ); | erase_if( std::inplace_vector<T, N>& c, Pred pred ); | ||
}} | }} | ||
| Line 126: | Line 126: | ||
std::cout << "After erase all 'a', 'r', and 't': " << std::quoted(word) << '\n'; | std::cout << "After erase all 'a', 'r', and 't': " << std::quoted(word) << '\n'; | ||
std::cout << "Erased symbols count: " << erased << '\n'; | std::cout << "Erased symbols count: " << erased << '\n'; | ||
| + | |||
| + | #if __cpp_lib_algorithm_default_value_type | ||
| + | std::erase(word, {'g'}); | ||
| + | std::cout << "After erase {'g'}: " << std::quoted(word) << '\n'; | ||
| + | #endif | ||
} | } | ||
| + | |p=true | ||
|output= | |output= | ||
Initially, word = "startling" | Initially, word = "startling" | ||
| Line 132: | Line 138: | ||
After erase all 'a', 'r', and 't': "sing" | After erase all 'a', 'r', and 't': "sing" | ||
Erased symbols count: 4 | Erased symbols count: 4 | ||
| + | After erase {'g'}: "sin" | ||
}} | }} | ||
|inplace_vector= | |inplace_vector= | ||
| Line 137: | Line 144: | ||
|code= | |code= | ||
#include <cassert> | #include <cassert> | ||
| + | #include <complex> | ||
#include <inplace_vector> | #include <inplace_vector> | ||
#include <numeric> | #include <numeric> | ||
| + | #include <print> | ||
int main() | int main() | ||
| Line 153: | Line 162: | ||
std::println("After erasing all even numbers, v = {}", v); | std::println("After erasing all even numbers, v = {}", v); | ||
std::println("Erased even numbers: {}", erased); | std::println("Erased even numbers: {}", erased); | ||
| + | |||
| + | std::inplace_vector<std::complex<double>> nums{<!---->{2, 2}, {4, 2}, {4, 8}, {4, 2}<!---->}; | ||
| + | std::erase(nums, {4, 2}); // since U = T, the value type can be ommited | ||
| + | std::println("After erase {4, 2}, nums = {}", nums); | ||
} | } | ||
|output= | |output= | ||
| Line 159: | Line 172: | ||
After erasing all even numbers, v = [1, 5, 7, 9] | After erasing all even numbers, v = [1, 5, 7, 9] | ||
Erased even numbers: 5 | Erased even numbers: 5 | ||
| + | After erase {4, 2}, nums = [(2,2), (4,8)] | ||
}} | }} | ||
| | | | ||
Latest revision as of 15:59, 22 September 2024
| Defined in header <inplace_vector>
|
||
| template< class T, std::size_t N, class U = T > constexpr typename std::inplace_vector<T, N>::size_type |
(1) | (since C++26) |
| template< class T, std::size_t N, class Pred > constexpr typename std::inplace_vector<T, N>::size_type |
(2) | (since C++26) |
1) Erases all elements that compare equal to value from the container. Equivalent to
auto it = std::remove(c.begin(), c.end(), value); auto r = std::distance(it, c.end()); c.erase(it, c.end()); return r;
2) Erases all elements that satisfy the predicate pred from the container. Equivalent to
auto it = std::remove_if(c.begin(), c.end(), pred); auto r = std::distance(it, c.end()); c.erase(it, c.end()); return r;
Contents |
[edit] Parameters
| c | - | container from which to erase |
| value | - | value to be removed |
| pred | - | unary predicate which returns true if the element should be erased. The expression pred(v) must be convertible to bool for every argument |
[edit] Return value
The number of erased elements.
[edit] Complexity
Linear.
[edit] Example
Run this code
#include <cassert> #include <complex> #include <inplace_vector> #include <numeric> #include <print> int main() { std::inplace_vector<int, 10> v(10, 0); std::ranges::iota(v, 0); std::println("Initially, v = {}", v); auto erased = std::erase(v, 3); std::println("After erase(v, 3), v = {}", v); assert(erased == 1); erased = std::erase_if(v, [](int x) { return x % 2 == 0; }); std::println("After erasing all even numbers, v = {}", v); std::println("Erased even numbers: {}", erased); std::inplace_vector<std::complex<double>> nums{{2, 2}, {4, 2}, {4, 8}, {4, 2}}; std::erase(nums, {4, 2}); // since U = T, the value type can be ommited std::println("After erase {4, 2}, nums = {}", nums); }
Output:
Initially, v = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
After erase(v, 3), v = [0, 1, 2, 4, 5, 6, 7, 8, 9]
After erasing all even numbers, v = [1, 5, 7, 9]
Erased even numbers: 5
After erase {4, 2}, nums = [(2,2), (4,8)][edit] See also
| removes elements satisfying specific criteria (function template) | |
| (C++20)(C++20) |
removes elements satisfying specific criteria (niebloid) |
