:list

[syntax] :list vars arg1 arg ...

[syntax] :string vars arg1 arg ...

[syntax] :vector vars arg1 arg ...

SRFI-42: Run through one or more lists, strings, or vectors. First all expressions in arg1 arg ... are evaluated and then all elements of the resulting values are enumerated from left to right. One can think of it as first appending all arguments and then enumerating the combined object. As a clarifying example, consider (list-ec (:string c (index i) "a" "b") (cons c i)) => ((#\a . 0) (#\b . 1)).