Clean up topological-sort
We don't actually need to get the full set of minimal elements on each iteration
because we don't need to break ties. It'll be faster (and cleaner) to just grab
the first one we find.
| author |
Steve Losh <steve@stevelosh.com> |
| date |
Sat, 26 Mar 2016 19:30:09 +0000 |
| parents |
d4ba6547d8a1
|
| children |
7447809d31ad
|
| branches/tags |
(none) |
| files |
src/wam/topological-sort.lisp |
Changes
--- a/src/wam/topological-sort.lisp Sat Mar 26 19:21:05 2016 +0000
+++ b/src/wam/topological-sort.lisp Sat Mar 26 19:30:09 2016 +0000
@@ -20,30 +20,28 @@
"
(labels
- ((find-minimal-elements (elements constraints)
- ;; An element is minimal if there are no other elements that are
- ;; required to precede it.
- (remove-if #'(lambda (element)
- (member (funcall key element)
- constraints
- :key #'cdr
- :test key-test))
- elements))
+ ((minimal-p (element constraints)
+ ;; An element is minimal if there are no other elements that must
+ ;; precede it.
+ (not (member (funcall key element) constraints
+ :key #'cdr
+ :test key-test)))
(in-constraint (val constraint)
;; Return whether val is either part of a constraint.
(or (funcall key-test val (car constraint))
(funcall key-test val (cdr constraint))))
(recur (remaining-constraints remaining-elements result)
- (let ((minimal-elements (find-minimal-elements remaining-elements
- remaining-constraints)))
- (if (null minimal-elements)
+ (let ((minimal-element
+ (find-if #'(lambda (el)
+ (minimal-p el remaining-constraints))
+ remaining-elements)))
+ (if (null minimal-element)
(if (null remaining-elements)
result
(error "Inconsistent constraints."))
- (let ((choice (car minimal-elements)))
- (recur (remove (funcall key choice)
- remaining-constraints
- :test #'in-constraint)
- (remove choice remaining-elements :test test)
- (cons choice result)))))))
+ (recur (remove (funcall key minimal-element)
+ remaining-constraints
+ :test #'in-constraint)
+ (remove minimal-element remaining-elements :test test)
+ (cons minimal-element result))))))
(reverse (recur constraints elements (list)))))