Syntax:
#include <algorithm> output_iterator transform( input_iterator start, input_iterator end, output_iterator result, UnaryFunction f ); output_iterator transform( input_iterator start1, input_iterator end1, input_iterator2 start2, output_iterator result, BinaryFunction f );
The transform algorithm applies the function f to some range of elements,
storing the result of each application of the function in result.
The first version of the function applies f to each element in [start,end) and
assigns the first output of the function to result, the second output to
(result+1), etc.
The second version of the transform works in a similar manner, except that it is given two ranges of elements and calls a binary function on a pair of elements.
For example, the following code uses transform to convert a string to uppercase using the toupper function:
string s("hello"); transform(s.begin(), s.end(), s.begin(), toupper); // in some compilers, you have to add a cast to "toupper" to resolve ambiguity: // transform(s.begin(), s.end(), s.begin(), (int (*)(int))toupper); cout << s << endl;
The above code displays the following output:
HELLO
Alternatively, the following example shows how user-defined functions can be used to transform a vector:
int increment(int i) { return ++i; } int sum(int a, int b) { return a+b; } int main() { vector<int> v1; for(int i=1; i<6; i++) v1.push_back (i*i); // v1: 1 4 9 16 25 vector<int> v2(v1.size()); transform(v1.begin(), v1.end(), v2.begin(), increment); // v2: 2 5 10 17 26 // add the elements of v1 and v2 together, store the result in v1 transform(v1.begin(), v1.end(), v2.begin(), v1.begin(), sum); // v1: 3 9 19 33 51 return 0; }