more mrb_flo_to_str fixes

- remove float check (take mrb_float instead of mrb_value)
- support -0.0
- fix range error if log10 is called when n == 0.0
- MSVC older than 2013: add signbit macro (for double)

include/mruby/numeric.h

@@ -16,7 +16,7 @@ extern "C" {
 #define FIXABLE(f) (POSFIXABLE(f) && NEGFIXABLE(f))
 
 mrb_value mrb_flo_to_fixnum(mrb_state *mrb, mrb_value val);
-mrb_value mrb_flo_to_str(mrb_state *mrb, mrb_value flo);
+mrb_value mrb_flo_to_str(mrb_state *mrb, mrb_float flo);
 
 mrb_value mrb_fixnum_to_str(mrb_state *mrb, mrb_value x, int base);
 

include/mruby/value.h

@@ -59,6 +59,7 @@ typedef short mrb_sym;
 #  include <float.h>
 #  define isnan _isnan
 #  define isinf(n) (!_finite(n) && !_isnan(n))
+#  define signbit(n) (_copysign(1.0, (n)) < 0.0)
 #  define strtoll _strtoi64
 #  define strtof (float)strtod
 #  define PRId32 "I32d"

src/numeric.c

@@ -107,17 +107,11 @@ num_div(mrb_state *mrb, mrb_value x)
  */
 
 mrb_value
-mrb_flo_to_str(mrb_state *mrb, mrb_value flo)
+mrb_flo_to_str(mrb_state *mrb, mrb_float flo)
 {
-  double n;
+  double n = (double)flo;
   int max_digits = FLO_MAX_DIGITS;
 
-  if (!mrb_float_p(flo)) {
-    mrb_raise(mrb, E_TYPE_ERROR, "non float value");
-  }
-
-  n = (double)mrb_float(flo);
-
   if (isnan(n)) {
     return mrb_str_new_lit(mrb, "NaN");
   }
@@ -137,12 +131,22 @@ mrb_flo_to_str(mrb_state *mrb, mrb_value flo)
     char s[48];
     char *c = &s[0];
 
-    if (n < 0) {
+    if (signbit(n)) {
       n = -n;
       *(c++) = '-';
     }
 
-    exp = (n > 1) ? floor(log10(n)) : -ceil(-log10(n));
+    if (n != 0.0) {
+      if (n > 1.0) {
+        exp = (int)floor(log10(n));
+      }
+      else {
+        exp = (int)-ceil(-log10(n));
+      }
+    }
+    else {
+      exp = 0;
+    }
 
     if ((exp < 0 ? -exp : exp) >= FLO_MAX_DIGITS) {
       /* exponent representation */
@@ -226,7 +230,7 @@ mrb_flo_to_str(mrb_state *mrb, mrb_value flo)
 static mrb_value
 flo_to_s(mrb_state *mrb, mrb_value flt)
 {
-  return mrb_flo_to_str(mrb, flt);
+  return mrb_flo_to_str(mrb, mrb_float(flt));
 }
 
 /* 15.2.9.3.2  */