code: function span(columns, math = settings.math) {
    const error = "You must pass a number greater than 0 for the number of columns.";
    let spanColumns = 0;
    let containerColumns = settings.columns;
  
    if (typeof columns === "string") {
      spanColumns = parseInt(columns.split(" of ")[0], 10);
  
      if (columns.split(" of ")[1]) {
        containerColumns = parseInt(columns.split(" of ")[1], 10);
      }
    } else if (typeof columns === "number" && columns) {
      spanColumns = columns;
    } else {
      throw new Error(error);
    }
  
    if (columns) {
      let columnWidth = spanColumns * settings.columnWidth;
      const gutters = (spanColumns - 1);
      const containerWidth = _updateContext(containerColumns);
  
      if (settings.gutterPosition === "before" ||
        settings.gutterPosition === "after" ||
        settings.gutterPosition === "split") {
        if (gutters) {
          columnWidth += (_calculateGutter() * gutters);
        }
      }
  
      if (settings.gutterPosition === "inside" ||
        settings.gutterPosition === "inside-static") {
        if (gutters) {
          columnWidth += (_calculateGutter()) * 2;
        } else {
          columnWidth += (_calculateGutter());
        }
      }
  
      if (math === "static") {
        return _staticCalculation(columnWidth);
      }
  
      if (math === "fluid") {
        return _percent(columnWidth, containerWidth);
      }
  
      return false;
    }
  
    return false;
  }
docs: Calculate a span width
  @param  {number|string} columns The number of columns; pass in an
  optional context
  @param  {string}        math    Type of calculation, "fluid" or "static";
  defaults to global settings
  @return {function}              Function to make calculation
  
  @usage
  // number, context is taken from global settings
  span(2);
  
  // string, context is taken from global settings, math overrides global settings
  span("2", "static");
  
  // string with new context, calculates based on a 6 column grid
  span("2 of 6");