1 files changed, 19 insertions, 0 deletions
diff --git a/guile/sat/helpers.scm b/guile/sat/helpers.scm
new file mode 100644
index 0000000..6729382
--- /dev/null
+++ b/guile/sat/helpers.scm
@@ -0,0 +1,19 @@
+(define-module (sat helpers)
+  #:use-module (sat solver)
+  #:use-module (srfi srfi-1)
+  #:export (exactly-one-true))
+
+(define (exactly-one-true v)
+
+  ;; At least one of 'v' must be true
+  (add-clause v)
+
+  ;; At least one of each pair in 'v' must be false
+  (pair-for-each
+    (lambda (v1p)
+      (for-each
+        (lambda (v2)
+          (add-clause (list (- (car v1p)) (- v2))))
+        (cdr v1p)))
+    v))
+