Capturing math in LUTs with JavaScript

cached_math.js

// save math functions in a table

const TAU = 2*Math.PI
const HALFPI = Math.PI / 2

const P = 10000 // precision factor, int arithmetic
const steps = 2048
const step = TAU/(steps)
const SIN_TABLE = []
for (let i=0;i<steps;i++) {
  const data = Math.sin(i*step)
  SIN_TABLE.push(Math.round(data*P))
}

const conversion = (steps*0.5)/Math.PI

const SIN = (n) => {
  const index = ((TAU+n)%TAU)*conversion
  return SIN_TABLE[Math.floor(index)]
}

const COS = (n) => {
  const index = ((HALFPI+TAU+n)%TAU)*conversion
  return SIN_TABLE[Math.floor(index)]
}

// Math.sin and Math.cos is a lot faster
// in most instances:
// https://jsben.ch/PpetH