More hacking for the signs of the outputs.

diff --git a/mp-gcd.c b/mp-gcd.c
index c772512..38f95d4 100644 (file)
--- a/mp-gcd.c
+++ b/mp-gcd.c
@@ -1,6 +1,6 @@
 /* -*-c-*-
  *
- * $Id: mp-gcd.c,v 1.3 1999/12/10 23:18:39 mdw Exp $
+ * $Id: mp-gcd.c,v 1.4 2000/06/17 11:34:46 mdw Exp $
  *
  * Extended GCD calculation
  *
@@ -30,6 +30,9 @@
 /*----- Revision history --------------------------------------------------* 
  *
  * $Log: mp-gcd.c,v $
+ * Revision 1.4  2000/06/17 11:34:46  mdw
+ * More hacking for the signs of the outputs.
+ *
  * Revision 1.3  1999/12/10 23:18:39  mdw
  * Change interface for suggested destinations.
  *
@@ -300,15 +303,32 @@ void mp_gcd(mp **gcd, mp **xx, mp **yy, mp *a, mp *b)
     /* --- Sort out the signs --- *
      *
      * Note that %$ax + by = a(x - b) + b(y + a)$%.
+     *
+     * This is currently bodgy.  It needs sorting out at some time.
      */
 
     if (yy) {
       if (y->f & MP_NEG) {
-       y = mp_add(y, y, a);
-       x = mp_sub(x, x, b);
+       do {
+         y = mp_add(y, y, a);
+         x = mp_sub(x, x, b);
+       } while (y->f & MP_NEG);
+      } else {
+       while (MP_CMP(y, >=, a)) {
+         y = mp_sub(y, y, a);
+         x = mp_add(x, x, b);
+       }
       }
-    } else if (x->f & MP_NEG)
-      x = mp_add(x, x, b);
+    } else {
+      if (x->f & MP_NEG) {
+       do
+         x = mp_add(x, x, b);
+       while (x->f & MP_NEG);
+      } else {
+       while (MP_CMP(x, >=, b))
+         x = mp_sub(x, x, b);
+      }
+    }
 
     /* --- Twiddle the signs --- */