From: "H.Yamamoto" <ocean@...2.ccsnet.ne.jp>
Date: 2004-05-10T13:36:54+09:00
Subject: Re: 5.000...007.to_s => "5"


Sorry for late posting. Does this patch solve your problem?

* numeric.c(flo_to_s): use DBL_DIG to show only significant digits.

Index: numeric.c
===================================================================
RCS file: /ruby/ruby/numeric.c,v
retrieving revision 1.107
diff -u -w -b -p -r1.107 numeric.c
--- numeric.c	7 May 2004 08:44:15 -0000	1.107
+++ numeric.c	10 May 2004 04:00:45 -0000
@@ -489,10 +489,9 @@ static VALUE
 flo_to_s(flt)
     VALUE flt;
 {
-    char buf[32];
-    char *fmt = "%.15f";
+    char fmt[sizeof(int)*3+10], buf[sizeof(double)*3+sizeof(int)*3+20];
     double value = RFLOAT(flt)->value;
-    double avalue, d1, d2;
+    int exp;
     char *p, *e;
 
     if (isinf(value))
@@ -500,13 +499,25 @@ flo_to_s(flt)
     else if(isnan(value))
 	return rb_str_new2("NaN");
 
-    avalue = fabs(value);
-    if (avalue < 1.0e-7 || avalue >= 1.0e15) {
-	fmt = "%.16e";
-    }    
+    sprintf(fmt, "%%.%de", DBL_DIG - 1);
     sprintf(buf, fmt, value);
-    if (!(e = strchr(buf, 'e'))) {
-	e = buf + strlen(buf);
+    e = strchr(buf, 'e');
+    exp = atoi(e+1);
+    if (-7 <= exp && exp < DBL_DIG - 1) {
+	char *d = strchr(buf, '.');
+	if (exp > 0) {
+	    memmove(d, d+1, exp);
+	    d[exp] = '.';
+	}
+	if (exp < 0) { /* needs room in `buf' for shifting (currently 7) */
+	    int n = -exp;
+	    d[0] = d[-1];
+	    memmove(d+n, d, strlen(d)+1);
+	    e += n;
+	    memset(buf, '0', n+1);
+	    buf[1] = '.';
+	}
+	*e = '\0';
     }
     p = e;
     while (*--p=='0')