remove_if用法

remove_if

function template

template < class ForwardIterator, class Predicate > ForwardIterator remove_if ( ForwardIterator first, ForwardIterator last, Predicate pred );

<algorithm>

Remove elements from range

Removes from the range [first,last) the elements for which pred applied to its value is true, and returns an iterator to the new end of the range, which now includes only the values for which pred was false.

The behavior of this function template is equivalent to:

template < class ForwardIterator, class Predicate > ForwardIterator remove_if ( ForwardIterator first, ForwardIterator last, Predicate pred ) { ForwardIterator result = first; for ( ; first != last; ++first) if (!pred(*first)) *result++ = *first; return result; }

Notice that this function does not alter the elements past the new end, which keep their old values and are still accessible.

Parameters

first, last

Forward iterators to the initial and final positions in a sequence. The range used is  [first,last), which contains all the elements between  first and  last, including the element pointed by  first but not the element pointed by  last.

pred

Unary predicate taking an element in the range as argument, and returning a value indicating the falsehood (with  false, or a zero value) or truth ( true, or non-zero) of some condition applied to it. This can either be a pointer to a function or an object whose class overloads  operator().

Return value

#include<iostream>
#include<algorithm>
#include<vector>
using namespace std;
class student{
	public:
		int key;
		int value;
	bool operator()(student s){
		if(s.value<2) return true;
			else return false;
}
};
int main(){
	vector<student>vec(4);
	vec[0].key=1;
	vec[0].value=1;
	vec[1].key=2;
	vec[1].value=2;
	vec[2].key=2;
	vec[2].value=2;
	vec[3].key=3;
	vec[3].value=3;
	vector<student>::iterator it,p;
	p=remove_if(vec.begin(),vec.end(),student());
	for(it=vec.begin();it!=p;it++)
		cout<<(*it).value<<endl;
}

A forward iterator pointing to the new end of the sequence, which now includes all the elements for which  pred was false.