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C++ Cookbook
book

C++ Cookbook

by D. Ryan Stephens, Christopher Diggins, Jonathan Turkanis, Jeff Cogswell
November 2005
Beginner to intermediate content levelBeginner to intermediate
594 pages
16h 23m
English
O'Reilly Media, Inc.
Content preview from C++ Cookbook

11.4. Filtering Values Outside a Given Range

Problem

You want to ignore values from a sequence that fall above or below a given range.

Solution

Use the remove_copy_if function found in the <algorithm>, as shown in Example 11-8.

Example 11-8. Removing elements from a sequence below a value

#include <algorithm>
#include <vector>
#include <iostream>
#include <iterator>

using namespace std;

struct OutOfRange
{
  OutOfRange(int min, int max)
    : min_(min), max_(max)
  { }
  bool operator()(int x) {
    return (x < min_) || (x > max_);
  }
  int min_;
  int max_;
};

int main()
{
  vector<int> v;
  v.push_back(6);
  v.push_back(12);
  v.push_back(18);
  v.push_back(24);
  v.push_back(30);
  remove_copy_if(v.begin(), v.end(),
    ostream_iterator<int>(cout, "\n"), OutOfRange(10,25));
}

The program in Example 11-8 produces the following output:

12
18
24

Discussion

The remove_copy_if function copies the elements from one container to another container (or output iterator), ignoring any elements that satisfy a predicate that you provide (it probably would have been more accurate if the function was named copy_ignore_if). The function, however, does not change the size of the target container. If, as is often the case, the number of elements copied by remove_copy_if is fewer than the size of the target container, you will have to shrink the target container by calling the erase member function.

The function remove_copy_if requires a unary predicate (a functor that takes one argument and returns a boolean value) that returns true when ...

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Publisher Resources

ISBN: 0596007612Supplemental ContentErrata Page