# File lib/sass/script/functions.rb, line 1494
    def str_insert(original, insert, index)
      assert_type original, :String, :string
      assert_type insert, :String, :insert
      assert_integer index, :index
      assert_unit index, nil, :index
      insertion_point = if index.to_i > 0
                          [index.to_i - 1, original.value.size].min
                        else
                          [index.to_i, -original.value.size - 1].max
                        end
      result = original.value.dup.insert(insertion_point, insert.value)
      Sass::Script::Value::String.new(result, original.type)
    end