From f5c47c467de7e52d73b94afc1bf3041c74a04fd1 Mon Sep 17 00:00:00 2001
From: Alex Shinn <alexshinn@gmail.com>
Date: Tue, 7 Jun 2016 22:43:49 +0900
Subject: [PATCH] preserve -0.0 when added to exact 0

---
 bignum.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/bignum.c b/bignum.c
index a34cea75..b94399cf 100644
--- a/bignum.c
+++ b/bignum.c
@@ -1202,7 +1202,7 @@ sexp sexp_add (sexp ctx, sexp a, sexp b) {
       r = sexp_make_fixnum(sum);
     break;
   case SEXP_NUM_FIX_FLO:
-    r = sexp_make_flonum(ctx, sexp_fixnum_to_double(a)+sexp_flonum_value(b));
+    r = a == SEXP_ZERO ? b : sexp_make_flonum(ctx, sexp_fixnum_to_double(a)+sexp_flonum_value(b));
     break;
   case SEXP_NUM_FIX_BIG:
     r = sexp_bignum_normalize(sexp_bignum_add_fixnum(ctx, b, a));