complex-sqrt/index.js

Floating point complex square root

'use strict';

module.exports = function ( a, b, output ) {
  output = output || []
  var w, absa, absb, boa, aob
  if( a==0 && b== 0 ) {
    output[0] = 0
    output[1] = 0
    return output
  } else if ((absa=Math.abs(a)) >= (absb=Math.abs(b))) {
    boa = b/a
    w = Math.sqrt(absa) * Math.sqrt((1+Math.sqrt(1+boa*boa))*0.5)
  } else {
    aob = a/b
    w = Math.sqrt(absb)*Math.sqrt(0.5*(Math.abs(aob) + Math.sqrt(1+aob*aob)))
  }

  if( w===0 ) {
    output[0] = 0
    output[1] = 0

  } else if (a > 0) {
    output[0] = w
    output[1] = 0.5*b/w

  } else if ( b >= 0 ) {
    output[0] = 0.5*absb/w
    output[1] = w

  } else {
    output[0] = 0.5*absb/w
    output[1] = -w

  }

  return output

}