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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

7.9. Transforming Elements in a Sequence

Problem

You have a sequence of elements and you have to do something to each one, either in place or as it is copied to another sequence.

Solution

Use the transform or for_each standard algorithms. Both are simple, but allow you to do almost anything you want to the elements in your sequence. See Example 7-9 for an illustration.

Example 7-9. Transforming data

#include <iostream>
#include <istream>
#include <string>
#include <list>
#include <algorithm>
#include <iterator>
#include <cctype>
#include "utils.h" // For printContainer(): see 7.10

using namespace std;

// Convert a string to upper case
string strToUpper(const string& s) {
   string tmp;
   for (string::const_iterator p = s.begin(); p != s.end(); ++p)
      tmp += toupper(*p);
   return(tmp);
}

string strAppend(const string& s1, const string& s2) {
   return(s1 + s2);
}

int main() {

   cout << "Enter a series of strings: ";
   istream_iterator<string> start(cin);
   istream_iterator<string> end;
   list<string> lst(start, end), out;

   // Use transform with an unary function...
   transform(lst.begin(), lst.end(),
             back_inserter(out),
             strToUpper);

   printContainer(out);

   cin.clear();

   cout << "Enter another series of strings: ";
   list<string> lst2(++start, end);
   out.clear();

   // ...or a binary function and another input sequence.
   transform(lst.begin(), lst.end(), lst2.begin(),
             back_inserter(out),
             strAppend);

   printContainer(out);
}

Discussion

The obvious function for transforming data is transform. It has two forms. The first form ...

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Publisher Resources

ISBN: 0596007612Supplemental ContentErrata Page