Function angle

external/.d3.js:10146–10148

(lambda0, lambda1)

// This is almost the same as (lambda1 - lambda0 + 360°) % 360°, except that we want
// the distance between ±180° to be 360°.
function angle(lambda0, lambda1) {
  return (lambda1 -= lambda0) < 0 ? lambda1 + 360 : lambda1;
}

function rangeCompare(a, b) {
  return a[0] - b[0];