# std::experimental::erase_if (std::map)

< cpp‎ | experimental

定义于头文件 `<experimental/map>` |  |
template <class Key, class T, class Compare, class Alloc, class Pred> void erase_if(std::map<Key,T,Compare,Alloc>& c, Pred pred); |  | (库基础 TS v2)

从容器擦除所有满足谓词 `pred` 的元素。等价于

    for (auto i = c.begin(), last = c.end(); i != last; ) {
      if (pred(*i)) {
        i = c.erase(i);
      } else {
        ++i;
      }
    }

### 参数

c | - | 要从中擦除的容器
pred | - | 确定该擦除哪些元素的谓词

### 复杂度

线性。

### 示例

    #include <experimental/map>
    #include <iostream>

    template<typename Os, typename Container>
    inline Os& operator<<(Os& os, Container const& cont)
    {
        os << "{";
        for (const auto& item : cont) {
            os << "{" << item.first << ", " << item.second << "}";
        }
        return os << "}";
    }

    int main()
    {
        std::map<int, char> data {{1, 'a'},{2, 'b'},{3, 'c'},{4, 'd'},
                                  {5, 'e'},{4, 'f'},{5, 'g'},{5, 'g'}};
        std::cout << "Original:\n" << data << '\n';

        std::experimental::erase_if(data, [](const auto& item) {
            return (item.first & 1) == 1;
        });

        std::cout << "Erase items with odd keys:\n" << data << '\n';
    }

输出：

    Original:
    {{1, a}{2, b}{3, c}{4, d}{5, e}}
    Erase items with odd keys:
    {{2, b}{4, d}}

### 参阅

remove remove_if | 移除满足特定判别标准的元素 (函数模板)