mapLinear<T extends num>  static method 
Implementation
static num mapLinear<T extends num>(T x, T a1, T a2, T b1, T b2) {
  return b1 + (x - a1) * (b2 - b1) / (a2 - a1);
}static num mapLinear<T extends num>(T x, T a1, T a2, T b1, T b2) {
  return b1 + (x - a1) * (b2 - b1) / (a2 - a1);
}