abs_most_negative_fixnum

abs_most_negative_fixnum

[Kevin Ryde]

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        * numbers.c (scm_quotient, scm_remainder): In inum/big, use mpz_cmp_ui
        for big == abs(most-negative-fixnum) special case.
        (abs_most_negative_fixnum): Remove, no longer used.

        * tests/numbers.test (quotient, remainder): Exercise inum/big at and
        near special case inum == fixnum-min, big == -fixnum-min.


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--- numbers.c.~1.229.~	2004-03-26 07:55:12.000000000 +1000
+++ numbers.c	2004-03-27 19:12:47.000000000 +1000
@@ -148,7 +148,6 @@
 
 \f
 
-static SCM abs_most_negative_fixnum;
 static mpz_t z_negative_one;
 
 \f
@@ -703,9 +702,13 @@
       else if (SCM_BIGP (y))
 	{
 	  if ((SCM_INUM (x) == SCM_MOST_NEGATIVE_FIXNUM)
-	      && (scm_i_bigcmp (abs_most_negative_fixnum, y) == 0))
-	    /* Special case:  x == fixnum-min && y == abs (fixnum-min) */
-	    return SCM_MAKINUM (-1);
+	      && (mpz_cmp_ui (SCM_I_BIG_MPZ (y),
+                              - SCM_MOST_NEGATIVE_FIXNUM) == 0))
+            {
+              /* Special case:  x == fixnum-min && y == abs (fixnum-min) */
+	      scm_remember_upto_here_1 (y);
+              return SCM_MAKINUM (-1);
+            }
 	  else
 	    return SCM_MAKINUM (0);
 	}
@@ -779,9 +782,13 @@
       else if (SCM_BIGP (y))
 	{
 	  if ((SCM_INUM (x) == SCM_MOST_NEGATIVE_FIXNUM)
-	      && (scm_i_bigcmp (abs_most_negative_fixnum, y) == 0))
-	    /* Special case:  x == fixnum-min && y == abs (fixnum-min) */
-	    return SCM_MAKINUM (0);
+	      && (mpz_cmp_ui (SCM_I_BIG_MPZ (y),
+                              - SCM_MOST_NEGATIVE_FIXNUM) == 0))
+            {
+              /* Special case:  x == fixnum-min && y == abs (fixnum-min) */
+	      scm_remember_upto_here_1 (y);
+              return SCM_MAKINUM (0);
+            }
 	  else
 	    return x;
 	}
@@ -5690,9 +5697,6 @@
 void
 scm_init_numbers ()
 {
-  abs_most_negative_fixnum = scm_i_long2big (- SCM_MOST_NEGATIVE_FIXNUM);
-  scm_permanent_object (abs_most_negative_fixnum);
-
   mpz_init_set_si (z_negative_one, -1);
 
   /* It may be possible to tune the performance of some algorithms by using

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--- numbers.test.~1.44.~	2004-03-26 07:45:06.000000000 +1000
+++ numbers.test	2004-03-27 19:11:43.000000000 +1000
@@ -324,7 +324,17 @@
       (eqv? 1 (quotient fixnum-min fixnum-min)))
 
     (pass-if "n = fixnum-min - 1"
-      (eqv? 0 (quotient fixnum-min (- fixnum-min 1)))))
+      (eqv? 0 (quotient fixnum-min (- fixnum-min 1))))
+
+    (pass-if "n = - fixnum-min - 1"
+      (eqv? -1 (quotient fixnum-min (1- (- fixnum-min)))))
+
+    ;; special case, normally inum/big is zero
+    (pass-if "n = - fixnum-min"
+      (eqv? -1 (quotient fixnum-min (- fixnum-min))))
+
+    (pass-if "n = - fixnum-min + 1"
+      (eqv? 0 (quotient fixnum-min (1+ (- fixnum-min))))))
 
   (with-test-prefix "(fixnum-min - 1) / n"
 
@@ -512,7 +522,17 @@
       (eqv? 0 (remainder fixnum-min fixnum-min)))
 
     (pass-if "n = fixnum-min - 1"
-      (eqv? fixnum-min (remainder fixnum-min (- fixnum-min 1)))))
+      (eqv? fixnum-min (remainder fixnum-min (- fixnum-min 1))))
+
+    (pass-if "n = - fixnum-min - 1"
+      (eqv? -1 (remainder fixnum-min (1- (- fixnum-min)))))
+
+    ;; special case, normally inum%big is the inum
+    (pass-if "n = - fixnum-min"
+      (eqv? 0 (remainder fixnum-min (- fixnum-min))))
+
+    (pass-if "n = - fixnum-min + 1"
+      (eqv? fixnum-min (remainder fixnum-min (1+ (- fixnum-min))))))
 
   (with-test-prefix "(fixnum-min - 1) / n"
 

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