src/sexagesimal.js
function modf (float) {
  const i = Math.trunc(float)
  const f = Math.abs(float - i)
  return [i, f]
}
function modf (float) {
  const i = Math.trunc(float)
  const f = Math.abs(float - i)
  return [i, f]
}
function modf ( float ) { const i = Math . trunc ( float ) const f = Math . abs ( float - i ) return [ i , f ] }
separate fix `i` from fraction `f`
@private
@param {Number} float
@returns {Array} [i, f]
{Number} i - (int) fix value
{Number} f - (float) fractional portion; always > 1
separate fix i from fraction f