position of an item in a string or a list
Major Section:  PROGRAMMING

(Position item seq) is the least index (zero-based) of the element item in the string or list seq, if in fact item is an element of seq. Otherwise (position item seq) is nil.

(Position-equal item lst) has a guard of (true-listp lst). Position-equal has the same functionality as the Common Lisp function position, except that it uses the equal function to test whether item is the same as each successive element of lst. See position and see position-eq.