modernize biglog() and biglog10()

1 files changed, 32 insertions, 20 deletions

diff --git a/big.c b/big.c
index 1e4eb33..24e5278 100644
--- a/big.c
+++ b/big.c
@@ -17,8 +17,6 @@
 #define MAX_INT_BITS		60
 #define LONG_LONG_OVERFLOW	(1ll<<MAX_INT_BITS)
 
-static double logIBASE;
-static double log10IBASE;
 word big_one;
 
 static word big_plus(word, word, int);
@@ -33,8 +31,6 @@ static word stimes(word, word);
 
 void bigsetup(void)
 {
-  logIBASE = log((double)IBASE);
-  log10IBASE = log10((double)IBASE);
   big_one = make(INT, 1, 0);
 }
 
@@ -677,28 +673,44 @@ word dbltobig(double x)
    the exact integers.  There are inherent deficiences in 64 bit fp,
    no point in trying to mask this */
 
-double biglog(x)		/* logarithm of big x */
-word x;
+static double big__log(word x, double logbase, const char *name, double (*fn)(double))
 {
   word n = 0;
   double r = digit(x);
-  if (big_is_negative(x) || bigzero(x))
-    errno = EDOM, math_error("log");
-  while (x = rest(x))
-    n++, r = digit(x) + r / IBASE;
-  return (log(r) + n * logIBASE);
+
+  if (big_is_negative(x) || bigzero(x)) {
+    errno = EDOM;
+    math_error(name);
+  }
+
+  while ((x = rest(x)) != 0) {
+    n++;
+    r = digit(x) + r / IBASE;
+  }
+
+  return (fn(r) + n * logbase);
 }
 
-double biglog10(x)		/* logarithm of big x */
-word x;
+/* logarithm of big x */
+double biglog(word x)
 {
-  word n = 0;
-  double r = digit(x);
-  if (big_is_negative(x) || bigzero(x))
-    errno = EDOM, math_error("log10");
-  while (x = rest(x))
-    n++, r = digit(x) + r / IBASE;
-  return (log10(r) + n * log10IBASE);
+  static double logIBASE = 0.0;
+  if (logIBASE == 0.0) {
+    logIBASE = log((double)IBASE);
+  }
+
+  return big__log(x, logIBASE, "log", log);
+}
+
+/* logarithm of big x */
+double biglog10(word x)
+{
+  static double log10IBASE = 0.0;
+  if (log10IBASE == 0.0) {
+    log10IBASE = log10((double)IBASE);
+  }
+
+  return big__log(x, log10IBASE, "log10", log10);
 }
 
 word bigscan(p)			/* read a big number (in decimal) */