Problem Statement

Given two ranges:   where:

Write a function/subroutine/... that takes two ranges and a real number, and returns the mapping of the real number from the first to the second range. Use this function to map values from the range   [0, 10]   to the range   [-1, 0].

Show additional idiomatic ways of performing the mapping, using tools available to the language.

Let's start with the solution:

import "/fmt" for Fmt

var mapRange = Fn.new { |a, b, s| b.from + (s - a.from) * (b.to - b.from) / (a.to - a.from) }

var a = 0..10
var b = -1..0
for (s in a) {
    var t = mapRange.call(a, b, s)
    var f = (t >= 0) ? " " : "" 
    System.print("%(Fmt.d(2, s)) maps to %(f)%(t)")
}