From 0e8a4ba4ee698bde17fc8357700fcdd0af4ed815 Mon Sep 17 00:00:00 2001
From: skilchen <skilchen@bluewin.ch>
Date: Thu, 31 May 2018 19:40:00 +0200
Subject: [PATCH 1/3] fix strformat handling of neg zero with sign

---
 lib/pure/strformat.nim      | 8 +++++++-
 tests/stdlib/tstrformat.nim | 4 +++-
 2 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/lib/pure/strformat.nim b/lib/pure/strformat.nim
index a8b128460782..87ee7fddb858 100644
--- a/lib/pure/strformat.nim
+++ b/lib/pure/strformat.nim
@@ -525,7 +525,13 @@ proc format*(value: SomeFloat; specifier: string; res: var string) =
 
   var f = formatBiggestFloat(value, fmode, spec.precision)
   if value >= 0.0 and spec.sign != '-':
-    f = spec.sign & f
+    if  value == 0.0:
+      if 1.0 / value == Inf:
+        # only add the sign if value != negZero
+        f = spec.sign & f
+    else:
+      f = spec.sign & f
+
   # the default for numbers is right-alignment:
   let align = if spec.align == '\0': '>' else: spec.align
   let result = alignString(f, spec.minimumWidth,
diff --git a/tests/stdlib/tstrformat.nim b/tests/stdlib/tstrformat.nim
index 4e5c614a7818..851328f62754 100644
--- a/tests/stdlib/tstrformat.nim
+++ b/tests/stdlib/tstrformat.nim
@@ -10,4 +10,6 @@ proc `$`(o: Obj): string = "foobar"
 
 var o: Obj
 doAssert fmt"{o}" == "foobar"
-doAssert fmt"{o:10}" == "foobar    "
\ No newline at end of file
+doAssert fmt"{o:10}" == "foobar    "
+
+doAssert fmt"{-0.0:g}" == "-0"
\ No newline at end of file

From 9caefe1f362c1b08cc9a148a62a4e36ceaeebb20 Mon Sep 17 00:00:00 2001
From: skilchen <skilchen@bluewin.ch>
Date: Thu, 31 May 2018 20:14:54 +0200
Subject: [PATCH 2/3] better tests for neg zero with sign

---
 tests/stdlib/tstrformat.nim | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/tests/stdlib/tstrformat.nim b/tests/stdlib/tstrformat.nim
index 851328f62754..e6ff12a1c867 100644
--- a/tests/stdlib/tstrformat.nim
+++ b/tests/stdlib/tstrformat.nim
@@ -12,4 +12,7 @@ var o: Obj
 doAssert fmt"{o}" == "foobar"
 doAssert fmt"{o:10}" == "foobar    "
 
-doAssert fmt"{-0.0:g}" == "-0"
\ No newline at end of file
+doAssert fmt"{-0.0:g}" == "-0"
+doassert fmt"{-0.0:+g}" == "-0"
+doAssert fmt"{0.0:g}" == "0"
+doAssert fmt"{0.0:+g}" == "+0"
\ No newline at end of file

From a2a25286d1e510b491a45e41b93d07e273be4761 Mon Sep 17 00:00:00 2001
From: skilchen <skilchen@bluewin.ch>
Date: Tue, 5 Jun 2018 02:01:59 +0200
Subject: [PATCH 3/3] use inplace insertion of the sign as suggested by
 Varriount

---
 lib/pure/strformat.nim | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/lib/pure/strformat.nim b/lib/pure/strformat.nim
index 16c703bb70b3..36404cdf7ca1 100644
--- a/lib/pure/strformat.nim
+++ b/lib/pure/strformat.nim
@@ -530,10 +530,10 @@ proc format*(value: SomeFloat; specifier: string; res: var string) =
       sign = true
       if  value == 0.0:
         if 1.0 / value == Inf:
-          # only add the sign if value != negZero
-          f = spec.sign & f
+          # only insert the sign if value != negZero
+          f.insert($spec.sign, 0)
       else:
-        f = spec.sign & f
+        f.insert($spec.sign, 0)
   else:
     sign = true