- &key error-if-not-found?)
- (declare (ignore error-if-not-found?))
- (search-for-match (vertex-edges vertex-1)
- (lambda (edge)
- (and (eq vertex-2 (other-vertex edge vertex-1))
- (funcall fn edge)))))
+ &key error-if-not-found?)
+ (let ((it (search-for-match (vertex-edges vertex-1)
+ (lambda (edge)
+ (and (eq vertex-2 (other-vertex edge vertex-1))
+ (funcall fn edge))))))
+ (when (and error-if-not-found? (not it))
+ (error 'graph-edge-not-found-error
+ :vertex-1 vertex-1 :vertex-2 vertex-1))
+ it))