On Fri, 26 Nov 2010 14:36:57 +0100, Pascal Costanza said:
Hi,
I just hacked the following macro:
(defmacro multiple-value-case (&body clauses) (when clauses (destructuring-bind (first &rest rest) clauses (cond ((member (first first) '(t otherwise)) (when clauses (warn "Dead code: ~S." clauses)) `(progn ,@(rest first))) (t (destructuring-bind ((&rest lambda-list) expression (guard) &rest body) first `(multiple-value-bind ,lambda-list ,expression (if ,guard (progn ,@body) (multiple-value-case ,@rest)))))))))
Did anybody see anything similar before? Any suggestions for improvement?
I am confused about why guard has parens around it. It might be better to group the guard and the body like cond does, i.e.
(destructuring-bind ((&rest lambda-list) expression (guard &rest body)) first
Also the nesting of the multiple-value-binds in the expansion leads to unexpected lexical scoping. Maybe if you call it multiple-value-cond* ...