From b0e3b873f5d33a750cc4b04a20a9e6634ece1a47 Mon Sep 17 00:00:00 2001
From: h2so5 <mail@h2so5.net>
Date: Sat, 22 Feb 2014 16:50:52 +0900
Subject: preserve significands in float-string conversion

---
 src/numeric.c | 19 ++++++++++++++++++-
 1 file changed, 18 insertions(+), 1 deletion(-)

(limited to 'src')

diff --git a/src/numeric.c b/src/numeric.c
index c17b9c251..a8c483148 100644
--- a/src/numeric.c
+++ b/src/numeric.c
@@ -143,8 +143,25 @@ mrb_flo_to_str(mrb_state *mrb, mrb_value flo)
     }
 
     exp = (n > 1) ? floor(log10(n)) : -ceil(-log10(n));
+    
+    /* preserve significands */
+    int length = 0;
+    if (exp < 0) {
+      int i, beg = -1, end = 0;
+      double f = n;
+      double fd = 0;
+      for (i = 0; i < FLO_MAX_DIGITS; ++i) {
+        f = (f - fd) * 10.0;
+        fd = floor(f + FLO_EPSILON);
+        if (fd != 0) {
+          if (beg < 0) beg = i;
+          end = i + 1;
+        }
+      }
+      if (beg >= 0) length = end - beg;
+    }
 
-    if ((exp < 0 ? -exp : exp) >= FLO_MAX_DIGITS) {
+    if (abs(exp) + length >= FLO_MAX_DIGITS) {
       /* exponent representation */
       e = TRUE;
       n = n / pow(10.0, exp);
-- 
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