Map range

Map range is a draft programming task. It is not yet considered ready to be promoted as a complete task, for reasons that should be found in its talk page.

Given two ranges [A1,A2], [B1,B2], and a value within range [A1,A2], map that value to its corresponding position within [B1,B2].

C++

This example defines a template function to handle the mapping, using two std::pair objects to define the source and destination ranges. It returns the provided value mapped into the target range.

It's not written efficiently; certainly, there can be fewer explicit temporary variables. The use of the template offers a choice in types for precision and accuracy considerations, though one area for improvement might be to allow a different type for intermediate calculations.

<lang cpp>#include <iostream>

1. include <utility>

template<typename tVal> tVal map_value(std::pair<tVal,tVal> a, std::pair<tVal, tVal> b, tVal inVal) {

 tVal inValNorm = inVal - a.first;
 tVal aUpperNorm = a.second - a.first;
 tVal normPosition = inValNorm / aUpperNorm;

 tVal bUpperNorm = b.second - b.first;
 tVal bValNorm = normPosition * bUpperNorm;
 tVal outVal = b.first + bValNorm;

 return outVal;

}

int main() {

 std::pair<float,float> a(0,10), b(-1,0);

 for(float value = 0.0; 10.0 >= value; ++value)
   std::cout << "map_value(" << value << ") = " << map_value(a, b, value) << std::endl;

 return 0;

}</lang>

Output:

map_value(0) = -1
map_value(1) = -0.9
map_value(2) = -0.8
map_value(3) = -0.7
map_value(4) = -0.6
map_value(5) = -0.5
map_value(6) = -0.4
map_value(7) = -0.3
map_value(8) = -0.2
map_value(9) = -0.1
map_value(10) = 0