((eq? head 'rotate-stencil) (interpret (caddr expr)))
((eq? head 'translate-stencil) (interpret (caddr expr)))
((eq? head 'combine-stencil)
- (for-each (lambda (e) (interpret e)) (cdr expr)))
+ (for-each interpret (cdr expr)))
(else
(collect (fold-false-pairs (strip-floats expr))))