Answer with best guess of what map could be
Based on the link you posted,
map should be provided by you and it should return the distance of the provided 3d position (first argument) and set the second argument to the color of the nearest object. If you don't know how to write such a function, I advise you to read this article.
Answer with the traditional meaning of map
map doesn't exist in neither glsl nor hlsl, but it's very easy to implement it.
The five arguments to a usual map function are
float map(float value, float min1, float max1, float min2, float max2)
it takes the value and converts it from the range defined by
max1 to the equivalent in the range defined by
max2. The implementation would look like this:
// Convert the current value to a percentage
// 0% - min1, 100% - max1
float perc = (value - min1) / (max1 - min1);
// Do the same operation backwards with min2 and max2
float value = perc * (max2 - min2) + min2;