move big_sub() to top to avoid redundant static decl, rename big__sub()

1 files changed, 99 insertions, 100 deletions

diff --git a/big.c b/big.c
index bbd1e38..5bf1772 100644
--- a/big.c
+++ b/big.c
@@ -40,7 +40,6 @@ struct big_div {
 
 word big_one;
 
-static word big_sub(word, word);
 static word len(word);
 static struct big_div big__longdiv(word, word);
 static struct big_div shortdiv(word, word);
@@ -50,7 +49,7 @@ static word shift(word, word);
 static word stimes(word, word);
 
 /* ignore input signs, treat x,y as positive */
-word big__plus(word x, word y, int signbit)
+static word big__plus(word x, word y, int signbit)
 {
   word d = digit0(x) + digit0(y);
   word r = make(INT, signbit | (d & MAXDIGIT), 0);	/* result */
@@ -88,6 +87,100 @@ word big__plus(word x, word y, int signbit)
   return r;
 }
 
+/* ignore input signs, treat x,y as positive */
+word big__sub(word x, word y)
+{
+  word d = digit0(x) - digit0(y);
+  word borrow = (d & IBASE) != 0;
+  word r = make(INT, d & MAXDIGIT, 0);	/* result */
+  word *z = &rest(r);
+  word *p = NULL;		/* pointer to trailing zeros, if any */
+  x = rest(x);
+  y = rest(y);
+
+  /* this loop has been unwrapped once, see above */
+  while (x && y) {
+    d = digit(x) - digit(y) - borrow;
+    borrow = (d & IBASE) != 0;
+    d = d & MAXDIGIT;
+    *z = make(INT, d, 0);
+
+    if (d) {
+      p = NULL;
+    } else if (!p) {
+      p = z;
+    }
+
+    x = rest(x);
+    y = rest(y);
+    z = &rest(*z);
+  }
+
+  /* at most one of these two loops will be invoked */
+  while (y) {
+    d = -digit(y) - borrow;
+    borrow = ((d & IBASE) != 0);
+    d = d & MAXDIGIT;
+    *z = make(INT, d, 0);
+
+    if (d) {
+      p = NULL;
+    } else if (!p) {
+      p = z;
+    }
+
+    y = rest(y);
+    z = &rest(*z);
+  }
+
+  /* alternative loop */
+  while (x) {
+    d = digit(x) - borrow;
+    borrow = ((d & IBASE) != 0);
+    d = d & MAXDIGIT;
+    *z = make(INT, d, 0);
+
+    if (d) {
+      p = NULL;
+    } else if (!p) {
+      p = z;
+    }
+
+    x = rest(x);
+    z = &rest(*z);
+  }
+
+  /* result is negative  - take complement and add 1 */
+  if (borrow) {
+    p = NULL;
+    d = (digit(r) ^ MAXDIGIT) + 1;
+    borrow = ((d & IBASE) != 0);	/* borrow now means `carry' (sorry) */
+    digit(r) = SIGNBIT | d;	/* set sign bit of result */
+    z = &rest(r);
+
+    while (*z) {
+      d = (digit(*z) ^ MAXDIGIT) + borrow;
+      borrow = ((d & IBASE) != 0);
+      digit(*z) = d = d & MAXDIGIT;
+
+      if (d) {
+	p = NULL;
+      } else if (!p) {
+	p = z;
+      }
+
+      z = &rest(*z);
+    }
+  }
+
+  /* remove redundant (ie trailing) zeros */
+  if (p) {
+    *p = 0;
+  }
+
+  return r;
+}
+
 void bigsetup(void)
 {
   big_one = make(INT, 1, 0);
@@ -161,11 +254,11 @@ word bigplus(word x, word y)
     if (big_is_positive(y)) {
       return (big__plus(x, y, 0));
     }
-    return (big_sub(x, y));
+    return (big__sub(x, y));
   }
 
   if (big_is_positive(y)) {
-    return (big_sub(y, x));
+    return (big__sub(y, x));
   }
 
   return (big__plus(x, y, SIGNBIT));	/* both negative */
@@ -176,7 +269,7 @@ word bigsub(word x, word y)
 {
   if (big_is_positive(x)) {
     if (big_is_positive(y)) {
-      return (big_sub(x, y));		/* both positive */
+      return (big__sub(x, y));		/* both positive */
     }
     return (big__plus(x, y, 0));		/* positive x, negative y */
   }
@@ -185,101 +278,7 @@ word bigsub(word x, word y)
     return (big__plus(x, y, SIGNBIT));	/* negative x, positive y */
   }
 
-  return (big_sub(y, x));	/* both negative */
-}
-
-/* ignore input signs, treat x,y as positive */
-word big_sub(word x, word y)
-{
-  word d = digit0(x) - digit0(y);
-  word borrow = (d & IBASE) != 0;
-  word r = make(INT, d & MAXDIGIT, 0);	/* result */
-  word *z = &rest(r);
-  word *p = NULL;		/* pointer to trailing zeros, if any */
-  x = rest(x);
-  y = rest(y);
-
-  /* this loop has been unwrapped once, see above */
-  while (x && y) {
-    d = digit(x) - digit(y) - borrow;
-    borrow = (d & IBASE) != 0;
-    d = d & MAXDIGIT;
-    *z = make(INT, d, 0);
-
-    if (d) {
-      p = NULL;
-    } else if (!p) {
-      p = z;
-    }
-
-    x = rest(x);
-    y = rest(y);
-    z = &rest(*z);
-  }
-
-  /* at most one of these two loops will be invoked */
-  while (y) {
-    d = -digit(y) - borrow;
-    borrow = ((d & IBASE) != 0);
-    d = d & MAXDIGIT;
-    *z = make(INT, d, 0);
-
-    if (d) {
-      p = NULL;
-    } else if (!p) {
-      p = z;
-    }
-
-    y = rest(y);
-    z = &rest(*z);
-  }
-
-  /* alternative loop */
-  while (x) {
-    d = digit(x) - borrow;
-    borrow = ((d & IBASE) != 0);
-    d = d & MAXDIGIT;
-    *z = make(INT, d, 0);
-
-    if (d) {
-      p = NULL;
-    } else if (!p) {
-      p = z;
-    }
-
-    x = rest(x);
-    z = &rest(*z);
-  }
-
-  /* result is negative  - take complement and add 1 */
-  if (borrow) {
-    p = NULL;
-    d = (digit(r) ^ MAXDIGIT) + 1;
-    borrow = ((d & IBASE) != 0);	/* borrow now means `carry' (sorry) */
-    digit(r) = SIGNBIT | d;	/* set sign bit of result */
-    z = &rest(r);
-
-    while (*z) {
-      d = (digit(*z) ^ MAXDIGIT) + borrow;
-      borrow = ((d & IBASE) != 0);
-      digit(*z) = d = d & MAXDIGIT;
-
-      if (d) {
-	p = NULL;
-      } else if (!p) {
-	p = z;
-      }
-
-      z = &rest(*z);
-    }
-  }
-
-  /* remove redundant (ie trailing) zeros */
-  if (p) {
-    *p = 0;
-  }
-
-  return r;
+  return (big__sub(y, x));	/* both negative */
 }
 
 /* returns +ve,0,-ve as x greater than, equal, less than y */