Function d3_transformNormalize

d3-3.2.8/d3.js:5233–5240

(a)

    return a[0] * b[0] + a[1] * b[1];
  }
  function d3_transformNormalize(a) {
    var k = Math.sqrt(d3_transformDot(a, a));
    if (k) {
      a[0] /= k;
      a[1] /= k;
    }
    return k;
  }
  function d3_transformCombine(a, b, k) {
    a[0] += k * b[0];
    a[1] += k * b[1];