d3.scale.ordinal = function() {

  return d3_scale_ordinal([], {t: "range", x: []});

};

function d3_scale_ordinal(domain, ranger) {

  var index,

      range,

      rangeBand;

  function scale(x) {

    return range[((index[x] || (index[x] = domain.push(x))) - 1) % range.length];

  }

  function steps(start, step) {

    return d3.range(domain.length).map(function(i) { return start + step * i; });

  }

  scale.domain = function(x) {

    if (!arguments.length) return domain;

    domain = [];

    index = {};

    var i = -1, n = x.length, xi;

    while (++i < n) if (!index[xi = x[i]]) index[xi] = domain.push(xi);

    return scale[ranger.t](ranger.x, ranger.p);

  };

  scale.range = function(x) {

    if (!arguments.length) return range;

    range = x;

    rangeBand = 0;

    ranger = {t: "range", x: x};

    return scale;

  };

  scale.rangePoints = function(x, padding) {

    if (arguments.length < 2) padding = 0;

    var start = x[0],

        stop = x[1],

        step = (stop - start) / (domain.length - 1 + padding);

    range = steps(domain.length < 2 ? (start + stop) / 2 : start + step * padding / 2, step);

    rangeBand = 0;

    ranger = {t: "rangePoints", x: x, p: padding};

    return scale;

  };

  scale.rangeBands = function(x, padding) {

    if (arguments.length < 2) padding = 0;

    var start = x[0],

        stop = x[1],

        step = (stop - start) / (domain.length + padding);

    range = steps(start + step * padding, step);

    rangeBand = step * (1 - padding);

    ranger = {t: "rangeBands", x: x, p: padding};

    return scale;

  };

  scale.rangeRoundBands = function(x, padding) {

    if (arguments.length < 2) padding = 0;

    var start = x[0],

        stop = x[1],

        step = Math.floor((stop - start) / (domain.length + padding));

    range = steps(start + Math.round((stop - start - (domain.length - padding) * step) / 2), step);

    rangeBand = Math.round(step * (1 - padding));

    ranger = {t: "rangeRoundBands", x: x, p: padding};

    return scale;

  };

  scale.rangeBand = function() {

    return rangeBand;

  };

  scale.copy = function() {

    return d3_scale_ordinal(domain, ranger);

  };

  return scale.domain(domain);

};