// ---------------------------------------------------------
// grid-calc
// Formula that calculates percentage of the column(s)
//
// Required arguments:
// `$number` Number
// `$columns` Number *predefined*
//
// Example of use:
// grid-calc(3, 12)
//
// @return String
// ---------------------------------------------------------
@function grid-calc ($number, $columns: $font-size-base) {
  @if type-of($number) != 'number' {
    @error 'The argument $number: `#{$number}` is of incorrect type: `#{type-of($number)}`. Type of `Number` is required!';
  }
  @else if type-of($columns) != 'number' {
    @error 'The argument $columns: `#{$columns}` is of incorrect type: `#{type-of($columns)}`. Type of `Number` is required!';
  }

  @return unquote((100 / $columns * $number) + '%');
}