factorial: Fix usage message to fit in with conventions.

[u/mdw/catacomb] / mpreduce.c

diff --git a/mpreduce.c b/mpreduce.c
index 7d31334..0f20ed8 100644 (file)
--- a/mpreduce.c
+++ b/mpreduce.c
@@ -1,6 +1,6 @@
 /* -*-c-*-
  *
- * $Id: mpreduce.c,v 1.2 2004/04/08 01:36:15 mdw Exp $
+ * $Id$
  *
  * Efficient reduction modulo nice primes
  *
@@ -47,12 +47,12 @@ DA_DECL(instr_v, mpreduce_instr);
  * Arguments:  @gfreduce *r@ = structure to fill in
  *             @mp *x@ = an integer
  *
- * Returns:    ---
+ * Returns:    Zero if successful; nonzero on failure.
  *
  * Use:                Initializes a context structure for reduction.
  */
 
-void mpreduce_create(mpreduce *r, mp *p)
+int mpreduce_create(mpreduce *r, mp *p)
 {
   mpscan sc;
   enum { Z = 0, Z1 = 2, X = 4, X0 = 6 };
@@ -64,7 +64,8 @@ void mpreduce_create(mpreduce *r, mp *p)
 
   /* --- Fill in the easy stuff --- */
 
-  assert(MP_ISPOS(p));
+  if (!MP_POSP(p))
+    return (-1);
   d = mp_bits(p);
   r->lim = d/MPW_BITS;
   r->s = d%MPW_BITS;
@@ -118,9 +119,9 @@ void mpreduce_create(mpreduce *r, mp *p)
     }
   }
   if ((DA(&iv)[DA_LEN(&iv) - 1].op & ~1u) == MPRI_SUB) {
-    fprintf(stderr,
-           "mpreduce can't handle moduli of the form 2^m + x\n");
-    abort();
+    mp_drop(r->p);
+    DA_DESTROY(&iv);
+    return (-1);
   }
 
 #undef INSTR
@@ -149,7 +150,8 @@ void mpreduce_create(mpreduce *r, mp *p)
       r->iv[i + r->in].argy = b;
     }
   }
-  DA_DESTROY(&iv);  
+  DA_DESTROY(&iv);
+  return (0);
 }
 
 /* --- @mpreduce_destroy@ --- *
@@ -253,7 +255,7 @@ mp *mpreduce_do(mpreduce *r, mp *d, mp *x)
 
   /* --- If source is negative, divide --- */
 
-  if (MP_ISNEG(x)) {
+  if (MP_NEGP(x)) {
     mp_div(0, &d, x, r->p);
     return (d);
   }
@@ -283,9 +285,9 @@ mp *mpreduce_do(mpreduce *r, mp *d, mp *x)
        *vl = 0;
        run(r->iv, il, vl, z);
 #ifdef DEBUG
-  MP_PRINTX("x", x);
-  mp_div(0, &_rr, x, r->p);
-  assert(MP_EQ(_r, _rr));
+       MP_PRINTX("x", x);
+       mp_div(0, &_rr, x, r->p);
+       assert(MP_EQ(_r, _rr));
 #endif
       }
     }
@@ -295,9 +297,9 @@ mp *mpreduce_do(mpreduce *r, mp *d, mp *x)
        *vl &= ((1 << r->s) - 1);
        run(r->iv + r->in, il + r->in, vl, z);
 #ifdef DEBUG
-  MP_PRINTX("x", x);
-  mp_div(0, &_rr, x, r->p);
-  assert(MP_EQ(_r, _rr));
+       MP_PRINTX("x", x);
+       mp_div(0, &_rr, x, r->p);
+       assert(MP_EQ(_r, _rr));
 #endif
       }
     }
@@ -335,12 +337,18 @@ mp *mpreduce_exp(mpreduce *mr, mp *d, mp *a, mp *e)
   mp *spare = (e->f & MP_BURN) ? MP_NEWSEC : MP_NEW;
 
   MP_SHRINK(e);
-  if (!MP_LEN(e))
+  MP_COPY(a);
+  if (MP_ZEROP(e))
     ;
-  else if (MP_LEN(e) < EXP_THRESH)
-    EXP_SIMPLE(x, a, e);
-  else
-    EXP_WINDOW(x, a, e);
+  else {
+    if (MP_NEGP(e))
+      a = mp_modinv(a, a, mr->p);
+    if (MP_LEN(e) < EXP_THRESH)
+      EXP_SIMPLE(x, a, e);
+    else
+      EXP_WINDOW(x, a, e);
+  }
+  mp_drop(a);
   mp_drop(d);
   mp_drop(spare);
   return (x);