# File lib/sass/script/value/list.rb, line 82 def self.assert_valid_index(list, n) if !n.int? || n.to_i == 0 raise ArgumentError.new("List index #{n} must be a non-zero integer") elsif list.to_a.size == 0 raise ArgumentError.new("List index is #{n} but list has no items") elsif n.to_i.abs > (size = list.to_a.size) raise ArgumentError.new( "List index is #{n} but list is only #{size} item#{'s' if size != 1} long") end end