src/utilities.lisp: Convert merge candidates to presentation form on the fly.

[sod] / src / utilities.lisp

diff --git a/src/utilities.lisp b/src/utilities.lisp
index b02fdf4..4935f8b 100644 (file)
--- a/src/utilities.lisp
+++ b/src/utilities.lisp
@@ -526,17 +526,21 @@
                         (cdddr neigh-record) best-path)))))))
     dead))
 
-(export '(inconsistent-merge-error merge-error-candidates))
+(export '(inconsistent-merge-error
+         merge-error-candidates merge-error-present-function))
 (define-condition inconsistent-merge-error (error)
   ((candidates :initarg :candidates
-              :reader merge-error-candidates))
+              :reader merge-error-candidates)
+   (present :initarg :present :initform #'identity
+           :reader merge-error-present-function))
   (:documentation
    "Reports an inconsistency in the arguments passed to `merge-lists'.")
   (:report (lambda (condition stream)
             (format stream "Merge inconsistency: failed to decide between ~
                             ~{~#[~;~A~;~A and ~A~:;~
                                  ~@{~A, ~#[~;and ~A~]~}~]~}"
-                    (merge-error-candidates condition)))))
+                    (mapcar (merge-error-present-function condition)
+                            (merge-error-candidates condition))))))
 
 (export 'merge-lists)
 (defun merge-lists (lists &key pick (test #'eql) (present #'identity))
@@ -593,7 +597,8 @@
                              candidates))
           (winner (cond ((null leasts)
                          (error 'inconsistent-merge-error
-                                :candidates (mapcar present candidates)))
+                                :candidates candidates
+                                :present present))
                         ((null (cdr leasts))
                          (car leasts))
                         (pick