Function steps

explainshell/web/static/js/d3.v3.js:6623–6627

(start, step)

      return range[((index.get(x) || index.set(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 = [];