one or more transformation functions
an input range
a range with each fun applied to all the elements. If there is more than one fun, the element type will be Tuple containing one element for each fun.
1 import std.algorithm.comparison : equal; 2 import std.range : chain; 3 int[] arr1 = [ 1, 2, 3, 4 ]; 4 int[] arr2 = [ 5, 6 ]; 5 auto squares = map!(a => a * a)(chain(arr1, arr2)); 6 assert(equal(squares, [ 1, 4, 9, 16, 25, 36 ]));
Multiple functions can be passed to map. In that case, the element type of map is a tuple containing one element for each function.
1 auto sums = [2, 4, 6, 8]; 2 auto products = [1, 4, 9, 16]; 3 4 size_t i = 0; 5 foreach (result; [ 1, 2, 3, 4 ].map!("a + a", "a * a")) 6 { 7 assert(result[0] == sums[i]); 8 assert(result[1] == products[i]); 9 ++i; 10 }
You may alias map with some function(s) to a symbol and use it separately:
1 import std.algorithm.comparison : equal; 2 import std.conv : to; 3 4 alias stringize = map!(to!string); 5 assert(equal(stringize([ 1, 2, 3, 4 ]), [ "1", "2", "3", "4" ]));
auto map(Range)(Range r) if (isInputRange!(Unqual!Range));
Implements the homonym function (also known as transform) present in many languages of functional flavor. The call map!(fun)(range) returns a range of which elements are obtained by applying fun(a) left to right for all elements a in range. The original ranges are not changed. Evaluation is done lazily.