过滤STL容器的现代方法? [英] Modern way to filter STL container?
问题描述
在使用了C#多年之后,我又回到C ++了,我想知道现代的-C ++ 11-过滤数组的方式,即,我们如何实现类似于此Linq查询的内容:
Coming back to C++ after years of C# I was wondering what the modern - read: C++11 - way of filtering an array would be, i.e. how can we achieve something similar to this Linq query:
var filteredElements = elements.Where(elm => elm.filterProperty == true);
为了过滤元素向量(字符串
出于这个问题)
In order to filter a vector of elements (strings
for the sake of this question)?
我真诚地希望使用旧的STL样式算法(甚至是扩展类,例如 boost :: filter_iterator
I sincerely hope the old STL style algorithms (or even extensions like boost::filter_iterator
) requiring explicit methods to be defined are superseded by now?
推荐答案
请参阅 code>),现在需要定义显式方法?来自cplusplus.com中的 std :: copy_if $ c $的示例c>
:
See the example from cplusplus.com for std::copy_if
:
std::vector<int> foo = {25,15,5,-5,-15};
std::vector<int> bar;
// copy only positive numbers:
std::copy_if (foo.begin(), foo.end(), std::back_inserter(bar), [](int i){return i>=0;} );
std :: copy_if
计算lambda表达式对于此处的 foo
中的每个元素,如果返回 true
,则将值复制到 bar
。
std::copy_if
evaluates the lambda expression for every element in foo
here and if it returns true
it copies the value to bar
.
std :: back_inserter
允许我们在末尾实际插入新元素 bar
(使用 push_back()
)的迭代器,而不必先将其调整为所需的大小。
The std::back_inserter
allows us to actually insert new elements at the end of bar
(using push_back()
) with an iterator without having to resize it to the required size first.
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