chickadee » srfi-189 » maybe-or

(maybe-or expr ...)syntax
(either-or expr ...)syntax

The exprs are evaluated in order. If an expr evaluates to a Just/Right, it is returned without evaluating any more expressions. Otherwise, the last Nothing/Left is returned. If there are no exprs, then Nothing / a Left of an unspecified value is returned. If an expr does not evaluate to a Maybe/Either, an error satisfying error-object is signaled.