Formal comment #69 (defect)

FIND delivers an ambiguous value
Reported by:	Nils M Holm

Component:	other
Version:	5.91

The FIND procedure described on page 63 can deliver an ambiguous
return value when applied to a list of booleans:

(find not '(#f)) => #f
(find not '(#t)) => #f

Proposed improvement: return the tail of the sublist beginning with
the first member satisfying the predicate:

(find not '(#t #f #t)) => (#f #t)
      (find not '(#f)) => (#f)
      (find not '(#t)) => #f

This modification would not only eliminate the ambiguity described
above but also make FIND more compatible to MEMBER and friends.

RESPONSE:

The `memp' procedure has exactly the semantics suggested for `find'.

The `find' procedure is the codification of a frequent usage for
`memp', and, as such, useful on its own.