Transform

Include <mln/core/ranges/view/transform.hpp>

1. template<class Func>
   auto view::transform(Range r, Func fun)
   

2. template<class Func>
   auto view::transform(Range r, Range r2, Func fun)
   

   param r:

   Input range

   param r2:

   Input range

   param fun:

   Function to apply on each element

   transform returns a view of the input range where fun is applied to the elements. The second version applies fun on elements of r as first argument and r2 as second argument. This view preserves the following properties:

   Properties	r	transform(r, fun)	transform(r, r2, fun)
   Segmented	X	X	X
   Forward	X	X	X
   Reversible	X	X	X
   Bidirectional	X	X	X
   Random Access	X	X	X
   Contiguous	X
   Writable	X	X*	X*

   (*): only if fun is a projection.

   Examples

   • Multiply all components by 2:

     mln::box2d box = {{0,0}, {2,3}};
     mln_foreach(auto p, ranges::view::transform(box, [](auto x) { return x*2; }))
       std::cout << p << ",";
     

     Outputs:

     (0,0),(0,2),(0,4),(2,0),(2,2),(2,4),
     

   • Write on the pair’s projected second member:

     std::vector<std::pair<int, int>> v = {{0,0}, {1, 1}, {2, 2}};
     mln_foreach(auto& second, ranges::view::transform(v, &std::pair<int, int>::second))
       second = -1;
     
     for(auto&& e : v)
       std::cout << e << ", "
     

     Outputs:

     (0,-1),(1,-1),(2,-1),
     

   • Operate on 2 ranges at the same time:

     mln::box2d box = {{0,0}, {2,3}};
     mln::box2d box2 = {{1,1}, {3,4}};
     auto adder = ranges::view::transform(box, box2, [](auto x, auto y) { return x+y; };
     mln_foreach(auto p, adder))
       std::cout << p << ",";
     

     Outputs:

     (1,1),(1,3),(1,5),(3,1),(3,3),(3,5),