Module: Sass::Script::Functions — Sass Documentation

@rachelnabors sprite-name gives us a list, index will return position of search in list, or false.

# File '/Users/jbolton/Projects/sass-site/.sass/lib/sass/script/functions.rb', line 286 def self.signature(method_name, arg_arity, kwarg_arity) return unless @signatures[method_name] @signatures[method_name].each do |signature| return signature if signature.args.size == arg_arity + kwarg_arity next unless signature.args.size < arg_arity + kwarg_arity # We have enough args. # Now we need to figure out which args are varargs # and if the signature allows them. t_arg_arity, t_kwarg_arity = arg_arity, kwarg_arity if signature.args.size > t_arg_arity # we transfer some kwargs arity to args arity # if it does not have enough args -- assuming the names will work out. t_kwarg_arity -= (signature.args.size - t_arg_arity) t_arg_arity = signature.args.size end if ( t_arg_arity == signature.args.size || t_arg_arity > signature.args.size && signature.var_args ) && (t_kwarg_arity == 0 |...

Full article: http://sass-lang.com/documentation/Sass/Script/Functions....