dudo/4_must_know_functions.md

## 4_must_know_functions.md

      
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              4_must_know_functions.md
            
          
    The 4 simple math functions

Lerp


Lerp is the acronym for linear interpolation. The idea is very simple, you have 2 values, and you want to “walk” between those values by a factor.

func lerp = (start, end, factor) => 
  start * (1-factor) + end * factor;
If you pass a factor of 0, you are pointing to the beginning of the walk so the value is equal to start.
If you pass a factor of 1, you are pointing to the end of the walk so the value is equal to end.
Any factor between 0 and 1 will add a (1-factor) of start argument and a factor of end argument. (e.g with start 0 and end 10 with a factor 0.5 you will have a 5, so the half of the path)
Normalize or Inverse Lerp

func normalize = (start, end, value) => 
  (value - start) / (end - start);
This function is the opposite of lerp. Instead of a range and a factor, we give a range and a value to find out the factor.
MapValue

func mapValue = (value, fromMin, fromMax, toMin, toMax) => { 
  const factor = normalize(fromMin, fromMax, value);
  return lerp(toMin, toMax, factor);
}
As you can see and guess it converts a value from the scale [fromMin, fromMax] to a value from the scale[toMin, toMax]. It’s just the normalize and lerp functions working together.
Clamp

func clamp = (value, min, max) => 
  Math.min(Math.max(value, min), max);
It limits the value to the scale [min, max]. Any value that is more than the max will turn max. If it’s less than min will turn min.