blocks|key|2781718|text|您可能正在寻找std::remove_if，其模式如下：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|2781719|vec.erase(std::remove_if(vec.begin(),+vec.end(),+predicate),+vec.end());|code-block|syntax|javascript|2781720|entityMap|0|LINK|mutability|MUTABLE|url|http://en.cppreference.com/w/cpp/algorithm/remove^0|7|E|7|E|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@$9|T|A|U|B|C]]|D|@$9|V|A|W|1|X]]|E|$]]|$1|F|3|G|5|H|7|Y|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|Z|8|@]|D|@]|E|$]]]|L|$M|$5|N|O|P|E|$Q|R]]]]

You're probably looking for <a href="http://en.cppreference.com/w/cpp/algorithm/remove" rel="noreferrer"><code>std::remove_if</code></a>, in a pattern such as:

<pre><code>vec.erase(std::remove_if(vec.begin(), vec.end(), predicate), vec.end());
</code></pre>

blocks|key|99576|text|它在Library+Fundamentals+v2中，很快就会在C%2B%2B20中。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|99577|entityMap|0|LINK|mutability|MUTABLE|url|http://en.cppreference.com/w/cpp/experimental/lib_extensions_2#Uniform_container_erasure|1|http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2018/p1209r0.html^0|2|N|0|W|5|1|0^^$0|@$1|2|3|4|5|6|7|N|8|@]|9|@$A|O|B|P|1|Q]|$A|R|B|S|1|T]]|C|$]]|$1|D|3|-4|5|6|7|U|8|@]|9|@]|C|$]]]|E|$F|$5|G|H|I|C|$J|K]]|L|$5|G|H|I|C|$J|M]]]]

It's in <a href="http://en.cppreference.com/w/cpp/experimental/lib_extensions_2#Uniform_container_erasure" rel="noreferrer">Library Fundamentals v2</a>, and soon in <a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2018/p1209r0.html" rel="noreferrer">C++20</a>.

blocks|key|2781777|text|我猜您正在考虑remove_if，它接受一个谓词来确定元素是否应该被删除。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|2781778|remove_if返回一个迭代器，指向容器中要删除的元素的开头。要实际删除它们，您需要使用erase|2781779|container.erase(remove_if(container.start(),+container.end(),+pred),+container.end())|code-block|syntax|javascript|2781780|2781781|可能是这样，也可能是您错误地回忆了copy_if算法？它不知何故被遗漏在标准之外，但却被写在--并在Effective+STL中实现--。|2781782|entityMap|0|LINK|mutability|MUTABLE|url|http://www.cplusplus.com/reference/algorithm/remove_if/|1|http://www.aristeia.com/books.html^0|7|9|7|9|0|0|0|9|19|5|0|0|0|H|7|1E|D|1|0^^$0|@$1|2|3|4|5|6|7|Z|8|@$9|10|A|11|B|C]]|D|@$9|12|A|13|1|14]]|E|$]]|$1|F|3|G|5|6|7|15|8|@$9|16|A|17|B|C]|$9|18|A|19|B|C]]|D|@]|E|$]]|$1|H|3|I|5|J|7|1A|8|@]|D|@]|E|$K|L]]|$1|M|3|-4|5|6|7|1B|8|@]|D|@]|E|$]]|$1|N|3|O|5|6|7|1C|8|@$9|1D|A|1E|B|C]]|D|@$9|1F|A|1G|1|1H]]|E|$]]|$1|P|3|-4|5|6|7|1I|8|@]|D|@]|E|$]]]|Q|$R|$5|S|T|U|E|$V|W]]|X|$5|S|T|U|E|$V|Y]]]]

I'm guessing you're thinking of <a href="http://www.cplusplus.com/reference/algorithm/remove_if/" rel="noreferrer"><code>remove_if</code></a> which takes a predicate to determine if the element ought to be removed.

<code>remove_if</code> returns an iterator pointing to the beginning of the elements to remove in the container. To actually remove them you need to use <code>erase</code>:

<pre><code>container.erase(remove_if(container.start(), container.end(), pred), container.end())
</code></pre>

<hr>

Either that or perhaps you mistakenly recalled the <code>copy_if</code> algorithm? Which somehow got left out of the standard but was written about - and implemented - in <a href="http://www.aristeia.com/books.html" rel="noreferrer">Effective STL</a>.

blocks|key|101362|text|MSVC还没有从P1209R0实现C%2B%2B20的std::erase_if，因此，作为一种变通方法，您可以将特定容器的实现从该纸张的某处复制到您的代码中。GCC+9.1和Clang+9.0已经有了。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|101363|namespace+std+{

//+for+std::string
template+<class+charT,+class+traits,+class+A,+class+Predicate>
void+erase_if(basic_string<charT,+traits,+A>&+c,+Predicate+pred)+{
++++c.erase(remove_if(c.begin(),+c.end(),+pred),+c.end());
}

//+for+std::deque
template+<class+T,+class+A,+class+Predicate>
void+erase_if(deque<T,+A>&+c,+Predicate+pred)+{
++++c.erase(remove_if(c.begin(),+c.end(),+pred),+c.end());
}

//+for+std::vector
template+<class+T,+class+A,+class+Predicate>
void+erase_if(vector<T,+A>&+c,+Predicate+pred)+{
++++c.erase(remove_if(c.begin(),+c.end(),+pred),+c.end());
}

//+for+std::list
template+<class+T,+class+A,+class+Predicate>
void+erase_if(list<T,+A>&+c,+Predicate+pred)+{
++++c.remove_if(pred);
}

//+for+std::forward_list
template+<class+T,+class+A,+class+Predicate>
void+erase_if(forward_list<T,+A>&+c,+Predicate+pred)+{
++++c.remove_if(pred);
}

//+for+std::map
template+<class+K,+class+T,+class+C,+class+A,+class+Predicate>
void+erase_if(map<K,+T,+C,+A>&+c,+Predicate+pred)+{
++++for+(auto+i+=+c.begin(),+last+=+c.end();+i+!=+last;+)
++++++++if+(pred(*i))
++++++++++++i+=+c.erase(i);
++++++++else
++++++++++++%2B%2Bi;
}

//+for+std::multimap
template+<class+K,+class+T,+class+C,+class+A,+class+Predicate>
void+erase_if(multimap<K,+T,+C,+A>&+c,+Predicate+pred)+{
++++for+(auto+i+=+c.begin(),+last+=+c.end();+i+!=+last;+)
++++++++if+(pred(*i))
++++++++++++i+=+c.erase(i);
++++++++else
++++++++++++%2B%2Bi;
}

//+for+std::set
template+<class+K,+class+C,+class+A,+class+Predicate>
void+erase_if(set<K,+C,+A>&+c,+Predicate+pred)+{
++++for+(auto+i+=+c.begin(),+last+=+c.end();+i+!=+last;+)
++++++++if+(pred(*i))
++++++++++++i+=+c.erase(i);
++++++++else
++++++++++++%2B%2Bi;
}

//+for+std::multiset
template+<class+K,+class+C,+class+A,+class+Predicate>
void+erase_if(multiset<K,+C,+A>&+c,+Predicate+pred)+{
++++for+(auto+i+=+c.begin(),+last+=+c.end();+i+!=+last;+)
++++++++if+(pred(*i))
++++++++++++i+=+c.erase(i);
++++++++else
++++++++++++%2B%2Bi;
}

//+for+std::unordered_map
template+<class+K,+class+T,+class+H,+class+P,+class+A,+class+Predicate>
void+erase_if(unordered_map<K,+T,+H,+P,+A>&+c,+Predicate+pred)+{
++++for+(auto+i+=+c.begin(),+last+=+c.end();+i+!=+last;+)
++++++++if+(pred(*i))
++++++++++++i+=+c.erase(i);
++++++++else
++++++++++++%2B%2Bi;
}

//+for+std::unordered_multimap
template+<class+K,+class+T,+class+H,+class+P,+class+A,+class+Predicate>
void+erase_if(unordered_multimap<K,+T,+H,+P,+A>&+c,+Predicate+pred)+{
++++for+(auto+i+=+c.begin(),+last+=+c.end();+i+!=+last;+)
++++++++if+(pred(*i))
++++++++++++i+=+c.erase(i);
++++++++else
++++++++++++%2B%2Bi;
}

//+for+std::unordered_set
template+<class+K,+class+H,+class+P,+class+A,+class+Predicate>
void+erase_if(unordered_set<K,+H,+P,+A>&+c,+Predicate+pred)+{
++++for+(auto+i+=+c.begin(),+last+=+c.end();+i+!=+last;+)
++++++++if+(pred(*i))
++++++++++++i+=+c.erase(i);
++++++++else
++++++++++++%2B%2Bi;
}

//+for+std::unordered_multiset
template+<class+K,+class+H,+class+P,+class+A,+class+Predicate>
void+erase_if(unordered_multiset<K,+H,+P,+A>&+c,+Predicate+pred)+{
++++for+(auto+i+=+c.begin(),+last+=+c.end();+i+!=+last;+)
++++++++if+(pred(*i))
++++++++++++i+=+c.erase(i);
++++++++else
++++++++++++%2B%2Bi;
}

}+//+namespace+std|code-block|syntax|javascript|101364|entityMap|0|LINK|mutability|MUTABLE|url|http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2018/p1209r0.html^0|N|D|8|7|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@$9|T|A|U|B|C]]|D|@$9|V|A|W|1|X]]|E|$]]|$1|F|3|G|5|H|7|Y|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|Z|8|@]|D|@]|E|$]]]|L|$M|$5|N|O|P|E|$Q|R]]]]

MSVC does not yet implement C++20's <code>std::erase_if</code> from <a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2018/p1209r0.html" rel="nofollow noreferrer">P1209R0</a> so, as a workaround, you can just copy the implementation for specific container from that paper somewhere to your code. GCC 9.1 and Clang 9.0 already have it.

<pre><code>namespace std {

// for std::string
template &lt;class charT, class traits, class A, class Predicate&gt;
void erase_if(basic_string&lt;charT, traits, A&gt;&amp; c, Predicate pred) {
 c.erase(remove_if(c.begin(), c.end(), pred), c.end());
}

// for std::deque
template &lt;class T, class A, class Predicate&gt;
void erase_if(deque&lt;T, A&gt;&amp; c, Predicate pred) {
 c.erase(remove_if(c.begin(), c.end(), pred), c.end());
}

// for std::vector
template &lt;class T, class A, class Predicate&gt;
void erase_if(vector&lt;T, A&gt;&amp; c, Predicate pred) {
 c.erase(remove_if(c.begin(), c.end(), pred), c.end());
}

// for std::list
template &lt;class T, class A, class Predicate&gt;
void erase_if(list&lt;T, A&gt;&amp; c, Predicate pred) {
 c.remove_if(pred);
}

// for std::forward_list
template &lt;class T, class A, class Predicate&gt;
void erase_if(forward_list&lt;T, A&gt;&amp; c, Predicate pred) {
 c.remove_if(pred);
}

// for std::map
template &lt;class K, class T, class C, class A, class Predicate&gt;
void erase_if(map&lt;K, T, C, A&gt;&amp; c, Predicate pred) {
 for (auto i = c.begin(), last = c.end(); i != last; )
 if (pred(*i))
 i = c.erase(i);
 else
 ++i;
}

// for std::multimap
template &lt;class K, class T, class C, class A, class Predicate&gt;
void erase_if(multimap&lt;K, T, C, A&gt;&amp; c, Predicate pred) {
 for (auto i = c.begin(), last = c.end(); i != last; )
 if (pred(*i))
 i = c.erase(i);
 else
 ++i;
}

// for std::set
template &lt;class K, class C, class A, class Predicate&gt;
void erase_if(set&lt;K, C, A&gt;&amp; c, Predicate pred) {
 for (auto i = c.begin(), last = c.end(); i != last; )
 if (pred(*i))
 i = c.erase(i);
 else
 ++i;
}

// for std::multiset
template &lt;class K, class C, class A, class Predicate&gt;
void erase_if(multiset&lt;K, C, A&gt;&amp; c, Predicate pred) {
 for (auto i = c.begin(), last = c.end(); i != last; )
 if (pred(*i))
 i = c.erase(i);
 else
 ++i;
}

// for std::unordered_map
template &lt;class K, class T, class H, class P, class A, class Predicate&gt;
void erase_if(unordered_map&lt;K, T, H, P, A&gt;&amp; c, Predicate pred) {
 for (auto i = c.begin(), last = c.end(); i != last; )
 if (pred(*i))
 i = c.erase(i);
 else
 ++i;
}

// for std::unordered_multimap
template &lt;class K, class T, class H, class P, class A, class Predicate&gt;
void erase_if(unordered_multimap&lt;K, T, H, P, A&gt;&amp; c, Predicate pred) {
 for (auto i = c.begin(), last = c.end(); i != last; )
 if (pred(*i))
 i = c.erase(i);
 else
 ++i;
}

// for std::unordered_set
template &lt;class K, class H, class P, class A, class Predicate&gt;
void erase_if(unordered_set&lt;K, H, P, A&gt;&amp; c, Predicate pred) {
 for (auto i = c.begin(), last = c.end(); i != last; )
 if (pred(*i))
 i = c.erase(i);
 else
 ++i;
}

// for std::unordered_multiset
template &lt;class K, class H, class P, class A, class Predicate&gt;
void erase_if(unordered_multiset&lt;K, H, P, A&gt;&amp; c, Predicate pred) {
 for (auto i = c.begin(), last = c.end(); i != last; )
 if (pred(*i))
 i = c.erase(i);
 else
 ++i;
}

} // namespace std
</code></pre>

blocks|key|99573|text|实际上，在pointer+containers的Boost库中存在一个名为erase_if的方法。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|99574|entityMap|0|LINK|mutability|MUTABLE|url|http://www.boost.org/doc/libs/1_43_0/libs/ptr_container/doc/ptr_sequence_adapter.html^0|11|8|5|I|0|0^^$0|@$1|2|3|4|5|6|7|N|8|@$9|O|A|P|B|C]]|D|@$9|Q|A|R|1|S]]|E|$]]|$1|F|3|-4|5|6|7|T|8|@]|D|@]|E|$]]]|G|$H|$5|I|J|K|E|$L|M]]]]

Actually there exists a method called <code>erase_if</code> in the Boost library for <a href="http://www.boost.org/doc/libs/1_43_0/libs/ptr_container/doc/ptr_sequence_adapter.html" rel="nofollow">pointer containers</a>.

blocks|key|2012988|text|有一个list::remove_if，但并不是所有的容器类都有。remove_if也是作为一种算法存在的，它可以与begin()和end()中的迭代器一起使用。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|2012989|entityMap^0|3|F|W|9|1L|7|1T|5|0^^$0|@$1|2|3|4|5|6|7|H|8|@$9|I|A|J|B|C]|$9|K|A|L|B|C]|$9|M|A|N|B|C]|$9|O|A|P|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|Q|8|@]|D|@]|E|$]]]|G|$]]

There is a <code>list::remove_if</code>, but not for all container classes. <code>remove_if</code> also exists as a algorithm, which can be used with the iterators you can get from <code>begin()</code> and <code>end()</code>.

blocks|key|4894507|text|使用新的C%2B%2B+20格式，您可以像这样使用它：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4894508|vector<int>+vec+{1,2,3,4,5};
auto+no_of_removed_elements+=+std::erase_if(vec,[](const+int+a){return+a==5;});|code-block|syntax|javascript|4894509|Link+to+the+reference.|offset|length|4894510|entityMap|0|LINK|mutability|MUTABLE|url|https://en.cppreference.com/w/cpp/container/vector/erase2^0|0|0|0|M|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|T|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|U|8|@]|9|@$I|V|J|W|1|X]]|A|$]]|$1|K|3|-4|5|6|7|Y|8|@]|9|@]|A|$]]]|L|$M|$5|N|O|P|A|$Q|R]]]]

With the new C++ 20 format you can use it like this:
<pre><code>vector&lt;int&gt; vec {1,2,3,4,5};
auto no_of_removed_elements = std::erase_if(vec,[](const int a){return a==5;});
</code></pre>
<a href="https://en.cppreference.com/w/cpp/container/vector/erase2" rel="nofollow noreferrer">Link to the reference.</a>

I've got a container and would like to erase elements based on a predicate. <code>erase_if</code> sounds familiar, but I can't find it in C++. What's the name and where is it defined?
I'd like to use it with a lambda in VS10.

Where is erase_if?

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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我有一个容器，想要擦除基于谓词的元素。erase_if听起来很熟悉，但我在C++中找不到它。它的名称是什么?它是在哪里定义的？我想把它和VS10中的lambda一起使用。

问erase_if在哪？
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问erase_if在哪？
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