Smallest key of a non-empty omap.
(head-key map) → *
This is used as an abbreviation, so it is enabled by default.
Function:
(defun head-key (map) (declare (xargs :guard (mapp map))) (declare (xargs :guard (not (emptyp map)))) (let ((__function__ 'head-key)) (declare (ignorable __function__)) (mv-let (key val) (head map) (declare (ignore val)) key)))