multiplying the elements in v with those in v2
#include <iostream>
#include <vector>
#include <algorithm>
#include <functional>
using namespace std;
int main()
{
vector<int> v, v2, result(10);
for(unsigned i=0; i < 10; ++i) v.push_back(i);
for(unsigned i=0; i < 10; ++i) v2.push_back(i);
transform(v.begin(), v.end(), v2.begin(), result.begin(), multiplies<int>());
return 0;
}std::transform with predicate
#include <iostream>
using std::cout;
using std::endl;
#include <algorithm>
#include <numeric>
#include <vector>
#include <iterator>
int calculateCube( int );
int main()
{
std::ostream_iterator< int > output( cout, " " );
int a2[ 10 ] = { 100, 2, 8, 1, 50, 3, 8, 8, 9, 10 };
std::vector< int > v2( a2, a2 + 10 ); // copy of a2
cout << "Vector v2 contains: ";
std::copy( v2.begin(), v2.end(), output );
std::vector< int > cubes( 10 ); // instantiate vector cubes
// calculate cube of each element in v; place results in cubes
std::transform( v2.begin(), v2.end(), cubes.begin(), calculateCube );
cout << "\n\nThe cube of every integer in Vector v is:\n";
std::copy( cubes.begin(), cubes.end(), output );
cout << endl;
return 0;
}
int calculateCube( int value )
{
return value * value * value;
}Vector v2 contains: 100 2 8 1 50 3 8 8 9 10
The cube of every integer in Vector v is:
1000000 8 512 1 125000 27 512 512 729 1000
Transform algorithm and list of integers
#include <iostream>
#include <list>
#include <algorithm>
using namespace std;
double reciprocal(double i) {
return 1.0/i;
}
int main(){
list<double> l;
int i;
for(i=1; i<10; i++)
l.push_back((double)i);
list<double>::iterator p = l.begin();
while(p != l.end()) {
cout << *p << endl;
p++;
}
p = transform(l.begin(), l.end(),l.begin(), reciprocal);
p = l.begin();
while(p != l.end()) {
cout << *p << endl;
p++;
}
return 0;
}Transform all elements into deque from set by multiplying 10
/* The following code example is taken from the book
* "The C++ Standard Library - A Tutorial and Reference"
* by Nicolai M. Josuttis, Addison-Wesley, 1999
*
* (C) Copyright Nicolai M. Josuttis 1999.
* Permission to copy, use, modify, sell and distribute this software
* is granted provided this copyright notice appears in all copies.
* This software is provided "as is" without express or implied
* warranty, and with no claim as to its suitability for any purpose.
*/
#include <iostream>
#include <set>
#include <deque>
#include <algorithm>
using namespace std;
/* PRINT_ELEMENTS()
* - prints optional C-string optcstr followed by
* - all elements of the collection coll
* - separated by spaces
*/
template <class T>
inline void PRINT_ELEMENTS (const T& coll, const char* optcstr="")
{
typename T::const_iterator pos;
std::cout << optcstr;
for (pos=coll.begin(); pos!=coll.end(); ++pos) {
std::cout << *pos << " ";
}
std::cout << std::endl;
}
int main()
{
set<int,greater<int> > coll1;
deque<int> coll2;
// insert elements from 1 to 9
for (int i=1; i<=9; ++i) {
coll1.insert(i);
}
PRINT_ELEMENTS(coll1,"initialized: ");
// transform all elements into coll2 by multiplying 10
transform (coll1.begin(),coll1.end(), // source
back_inserter(coll2), // destination
bind2nd(multiplies<int>(),10)); // operation
PRINT_ELEMENTS(coll2,"transformed: ");
}initialized: 9 8 7 6 5 4 3 2 1
transformed: 90 80 70 60 50 40 30 20 10
Transform array to pair
#include <algorithm>
#include <iostream>
#include <iterator>
#include <string>
#include <vector>
#include <utility>
using namespace std;
typedef pair<int,string> Pair;
inline bool less_than_second( const Pair& b1, const Pair& b2 ){
return b1.second < b2.second;
}
int main( )
{
const char* names[] = { "A","B", "C", "D","E" };
const int values[] = { 18, 20, 26, 30, 41 };
const int num_pairs = sizeof( names ) / sizeof( names[0] );
vector<Pair> pair( num_pairs );
transform( values, values+num_pairs, names,pair.begin(), make_pair<int,string> );
if( pair[1].first > pair[3].first )
cout << pair[1].second << " > " << pair[3].second << endl;
else if( pair[1].first == pair[3].first )
cout << pair[1].second << " == " << pair[3].second << endl;
else
cout << pair[1].second << " < " << pair[3].second << endl;
}Transform v, putting the result into a new sequence
#include <iostream>
#include <vector>
#include <algorithm>
#include <functional>
using namespace std;
// A function object that computes a reciprocal.
class reciprocal : unary_function<double, double> {
public:
result_type sum;
result_type operator()(argument_type val) {
if(val == 0.0) return 0.0;
return 1.0 / val; // return reciprocal
}
};
int main(){
int i;
vector<double> v;
for(i=1; i < 10; ++i) v.push_back((double)i);
vector<double> v2(10);
transform(v.begin(), v.end(), v2.begin(), reciprocal());
return 0;
}Use generic template function with transform
/* The following code example is taken from the book
* "C++ Templates - The Complete Guide"
* by David Vandevoorde and Nicolai M. Josuttis, Addison-Wesley, 2002
*
* (C) Copyright David Vandevoorde and Nicolai M. Josuttis 2002.
* Permission to copy, use, modify, sell and distribute this software
* is granted provided this copyright notice appears in all copies.
* This software is provided "as is" without express or implied
* warranty, and with no claim as to its suitability for any purpose.
*/
#include <iostream>
using namespace std;
template <typename T, int VAL>
T addValue (T const& x)
{
return x + VAL;
}
void call_addValue()
{
addValue<int,5>(42);
}
template <typename IT, typename OP>
void transform (IT beg, IT end, IT to, OP op)
{
while (beg != end) {
*to++ = op(*beg++);
}
}
int main()
{
call_addValue();
int m[] = { 1, 2, 3, 4, 5, 6 };
transform (m, m+6,
m,
(int(*)(int const&)) // cast necessary
addValue<int,5>);
for(int i=0;i<6;i++){
cout << m[i] << " ";
}
}6 7 8 9 10 11 "
Use transform function to square all elements in an array
/* The following code example is taken from the book
* "The C++ Standard Library - A Tutorial and Reference"
* by Nicolai M. Josuttis, Addison-Wesley, 1999
*
* (C) Copyright Nicolai M. Josuttis 1999.
* Permission to copy, use, modify, sell and distribute this software
* is granted provided this copyright notice appears in all copies.
* This software is provided "as is" without express or implied
* warranty, and with no claim as to its suitability for any purpose.
*/
#include <iostream>
#include <algorithm>
#include <functional>
#include <iterator>
using namespace std;
int main()
{
int coll[] = { 5, 6, 2, 4, 1, 3 };
// square all elements
transform (coll, coll+6, // first source
coll, // second source
coll, // destination
multiplies<int>()); // operation
// print all elements
copy (coll, coll+6,
ostream_iterator<int>(cout," "));
cout << endl;
}25 36 4 16 1 9
Use transform to add each element traversed forward with each element traversed backward
/* The following code example is taken from the book
* "The C++ Standard Library - A Tutorial and Reference"
* by Nicolai M. Josuttis, Addison-Wesley, 1999
*
* (C) Copyright Nicolai M. Josuttis 1999.
* Permission to copy, use, modify, sell and distribute this software
* is granted provided this copyright notice appears in all copies.
* This software is provided "as is" without express or implied
* warranty, and with no claim as to its suitability for any purpose.
*/
#include <iostream>
#include <vector>
#include <deque>
#include <list>
#include <set>
#include <map>
#include <string>
#include <algorithm>
#include <iterator>
#include <functional>
#include <numeric>
/* PRINT_ELEMENTS()
* - prints optional C-string optcstr followed by
* - all elements of the collection coll
* - separated by spaces
*/
template <class T>
inline void PRINT_ELEMENTS (const T& coll, const char* optcstr="")
{
typename T::const_iterator pos;
std::cout << optcstr;
for (pos=coll.begin(); pos!=coll.end(); ++pos) {
std::cout << *pos << " ";
}
std::cout << std::endl;
}
/* INSERT_ELEMENTS (collection, first, last)
* - fill values from first to last into the collection
* - NOTE: NO half-open range
*/
template <class T>
inline void INSERT_ELEMENTS (T& coll, int first, int last)
{
for (int i=first; i<=last; ++i) {
coll.insert(coll.end(),i);
}
}
using namespace std;
int main()
{
vector<int> coll1;
list<int> coll2;
INSERT_ELEMENTS(coll1,1,9);
PRINT_ELEMENTS(coll1,"coll1: ");
/* add each element traversed forward with each element traversed backward
* and insert result into coll2
*/
transform (coll1.begin(), coll1.end(), // first source range
coll1.rbegin(), // second source range
back_inserter(coll2), // destination range
plus<int>()); // operation
PRINT_ELEMENTS(coll2,"coll2: ");
}coll1: 1 2 3 4 5 6 7 8 9
coll2: 10 10 10 10 10 10 10 10 10
Use transform to negate all elements in a container
/* The following code example is taken from the book
* "The C++ Standard Library - A Tutorial and Reference"
* by Nicolai M. Josuttis, Addison-Wesley, 1999
*
* (C) Copyright Nicolai M. Josuttis 1999.
* Permission to copy, use, modify, sell and distribute this software
* is granted provided this copyright notice appears in all copies.
* This software is provided "as is" without express or implied
* warranty, and with no claim as to its suitability for any purpose.
*/
#include <iostream>
#include <vector>
#include <deque>
#include <list>
#include <set>
#include <map>
#include <string>
#include <algorithm>
#include <iterator>
#include <functional>
#include <numeric>
/* PRINT_ELEMENTS()
* - prints optional C-string optcstr followed by
* - all elements of the collection coll
* - separated by spaces
*/
template <class T>
inline void PRINT_ELEMENTS (const T& coll, const char* optcstr="")
{
typename T::const_iterator pos;
std::cout << optcstr;
for (pos=coll.begin(); pos!=coll.end(); ++pos) {
std::cout << *pos << " ";
}
std::cout << std::endl;
}
/* INSERT_ELEMENTS (collection, first, last)
* - fill values from first to last into the collection
* - NOTE: NO half-open range
*/
template <class T>
inline void INSERT_ELEMENTS (T& coll, int first, int last)
{
for (int i=first; i<=last; ++i) {
coll.insert(coll.end(),i);
}
}
using namespace std;
int main()
{
vector<int> coll1;
list<int> coll2;
INSERT_ELEMENTS(coll1,1,9);
PRINT_ELEMENTS(coll1,"coll1: ");
// negate all elements in coll1
transform (coll1.begin(), coll1.end(), // source range
coll1.begin(), // destination range
negate<int>()); // operation
PRINT_ELEMENTS(coll1,"negated: ");
}coll1: 1 2 3 4 5 6 7 8 9
negated: -1 -2 -3 -4 -5 -6 -7 -8 -9
Use transform to print differences of two corresponding elements
/* The following code example is taken from the book
* "The C++ Standard Library - A Tutorial and Reference"
* by Nicolai M. Josuttis, Addison-Wesley, 1999
*
* (C) Copyright Nicolai M. Josuttis 1999.
* Permission to copy, use, modify, sell and distribute this software
* is granted provided this copyright notice appears in all copies.
* This software is provided "as is" without express or implied
* warranty, and with no claim as to its suitability for any purpose.
*/
#include <iostream>
#include <vector>
#include <deque>
#include <list>
#include <set>
#include <map>
#include <string>
#include <algorithm>
#include <iterator>
#include <functional>
#include <numeric>
/* PRINT_ELEMENTS()
* - prints optional C-string optcstr followed by
* - all elements of the collection coll
* - separated by spaces
*/
template <class T>
inline void PRINT_ELEMENTS (const T& coll, const char* optcstr="")
{
typename T::const_iterator pos;
std::cout << optcstr;
for (pos=coll.begin(); pos!=coll.end(); ++pos) {
std::cout << *pos << " ";
}
std::cout << std::endl;
}
/* INSERT_ELEMENTS (collection, first, last)
* - fill values from first to last into the collection
* - NOTE: NO half-open range
*/
template <class T>
inline void INSERT_ELEMENTS (T& coll, int first, int last)
{
for (int i=first; i<=last; ++i) {
coll.insert(coll.end(),i);
}
}
using namespace std;
int main()
{
vector<int> coll1;
list<int> coll2;
INSERT_ELEMENTS(coll1,1,9);
PRINT_ELEMENTS(coll1,"coll1: ");
// print differences of two corresponding elements
cout << "diff: ";
transform (coll1.begin(), coll1.end(), // first source range
coll2.begin(), // second source range
ostream_iterator<int>(cout, " "), // destination range
minus<int>()); // operation
cout << endl;
}coll1: 1 2 3 4 5 6 7 8 9
diff: 2 3 4 5 6 7 8 9 10
Use transform to print elements negatively and in reverse order
/* The following code example is taken from the book
* "The C++ Standard Library - A Tutorial and Reference"
* by Nicolai M. Josuttis, Addison-Wesley, 1999
*
* (C) Copyright Nicolai M. Josuttis 1999.
* Permission to copy, use, modify, sell and distribute this software
* is granted provided this copyright notice appears in all copies.
* This software is provided "as is" without express or implied
* warranty, and with no claim as to its suitability for any purpose.
*/
#include <iostream>
#include <vector>
#include <deque>
#include <list>
#include <set>
#include <map>
#include <string>
#include <algorithm>
#include <iterator>
#include <functional>
#include <numeric>
/* PRINT_ELEMENTS()
* - prints optional C-string optcstr followed by
* - all elements of the collection coll
* - separated by spaces
*/
template <class T>
inline void PRINT_ELEMENTS (const T& coll, const char* optcstr="")
{
typename T::const_iterator pos;
std::cout << optcstr;
for (pos=coll.begin(); pos!=coll.end(); ++pos) {
std::cout << *pos << " ";
}
std::cout << std::endl;
}
/* INSERT_ELEMENTS (collection, first, last)
* - fill values from first to last into the collection
* - NOTE: NO half-open range
*/
template <class T>
inline void INSERT_ELEMENTS (T& coll, int first, int last)
{
for (int i=first; i<=last; ++i) {
coll.insert(coll.end(),i);
}
}
using namespace std;
int main()
{
vector<int> coll1;
list<int> coll2;
INSERT_ELEMENTS(coll1,1,9);
PRINT_ELEMENTS(coll1,"coll1: ");
// print coll2 negatively and in reverse order
transform (coll2.rbegin(), coll2.rend(), // source range
ostream_iterator<int>(cout," "), // destination range
negate<int>()); // operation
cout << endl;
}coll1: 1 2 3 4 5 6 7 8 9
Use transform to square each element
/* The following code example is taken from the book
* "The C++ Standard Library - A Tutorial and Reference"
* by Nicolai M. Josuttis, Addison-Wesley, 1999
*
* (C) Copyright Nicolai M. Josuttis 1999.
* Permission to copy, use, modify, sell and distribute this software
* is granted provided this copyright notice appears in all copies.
* This software is provided "as is" without express or implied
* warranty, and with no claim as to its suitability for any purpose.
*/
#include <iostream>
#include <vector>
#include <deque>
#include <list>
#include <set>
#include <map>
#include <string>
#include <algorithm>
#include <iterator>
#include <functional>
#include <numeric>
/* PRINT_ELEMENTS()
* - prints optional C-string optcstr followed by
* - all elements of the collection coll
* - separated by spaces
*/
template <class T>
inline void PRINT_ELEMENTS (const T& coll, const char* optcstr="")
{
typename T::const_iterator pos;
std::cout << optcstr;
for (pos=coll.begin(); pos!=coll.end(); ++pos) {
std::cout << *pos << " ";
}
std::cout << std::endl;
}
/* INSERT_ELEMENTS (collection, first, last)
* - fill values from first to last into the collection
* - NOTE: NO half-open range
*/
template <class T>
inline void INSERT_ELEMENTS (T& coll, int first, int last)
{
for (int i=first; i<=last; ++i) {
coll.insert(coll.end(),i);
}
}
using namespace std;
int main()
{
vector<int> coll1;
list<int> coll2;
INSERT_ELEMENTS(coll1,1,9);
PRINT_ELEMENTS(coll1,"coll1: ");
// square each element
transform (coll1.begin(), coll1.end(), // first source range
coll1.begin(), // second source range
coll1.begin(), // destination range
multiplies<int>()); // operation
PRINT_ELEMENTS(coll1,"squared: ");
}coll1: 1 2 3 4 5 6 7 8 9
squared: 1 4 9 16 25 36 49 64 81
Use transform to transform elements in one container into another container with ten times their value
/* The following code example is taken from the book
* "The C++ Standard Library - A Tutorial and Reference"
* by Nicolai M. Josuttis, Addison-Wesley, 1999
*
* (C) Copyright Nicolai M. Josuttis 1999.
* Permission to copy, use, modify, sell and distribute this software
* is granted provided this copyright notice appears in all copies.
* This software is provided "as is" without express or implied
* warranty, and with no claim as to its suitability for any purpose.
*/
#include <iostream>
#include <vector>
#include <deque>
#include <list>
#include <set>
#include <map>
#include <string>
#include <algorithm>
#include <iterator>
#include <functional>
#include <numeric>
/* PRINT_ELEMENTS()
* - prints optional C-string optcstr followed by
* - all elements of the collection coll
* - separated by spaces
*/
template <class T>
inline void PRINT_ELEMENTS (const T& coll, const char* optcstr="")
{
typename T::const_iterator pos;
std::cout << optcstr;
for (pos=coll.begin(); pos!=coll.end(); ++pos) {
std::cout << *pos << " ";
}
std::cout << std::endl;
}
/* INSERT_ELEMENTS (collection, first, last)
* - fill values from first to last into the collection
* - NOTE: NO half-open range
*/
template <class T>
inline void INSERT_ELEMENTS (T& coll, int first, int last)
{
for (int i=first; i<=last; ++i) {
coll.insert(coll.end(),i);
}
}
using namespace std;
int main()
{
vector<int> coll1;
list<int> coll2;
INSERT_ELEMENTS(coll1,1,9);
PRINT_ELEMENTS(coll1,"coll1: ");
// transform elements of coll1 into coll2 with ten times their value
transform (coll1.begin(), coll1.end(), // source range
back_inserter(coll2), // destination range
bind2nd(multiplies<int>(),10)); // operation
PRINT_ELEMENTS(coll2,"coll2: ");
}coll1: 1 2 3 4 5 6 7 8 9
coll2: 10 20 30 40 50 60 70 80 90
