function d3_scale_polylinear(domain, range, uninterpolate, interpolate) {
  var u = [],
      i = [],
      j = 0,
      k = domain.length - 1;

  // Handle descending domains.
  if (domain[k] < domain[0]) {
    domain = domain.slice().reverse();
    range = range.slice().reverse();
  }

  while (++j <= k) {
    u.push(uninterpolate(domain[j - 1], domain[j]));
    i.push(interpolate(range[j - 1], range[j]));
  }

  return function(x) {
    var j = d3.bisect(domain, x, 1, k) - 1;
    return i[j](u[j](x));
  };
}
