seq: fix incorrect output with start or end of -0

* src/seq.c (main): Avoid seq_fast() with a start or end of -0.
* tests/misc/seq.pl: Add test cases.
* NEWS: Mention the fix.
Fixes http://bugs.gnu.org/17800

1 files changed, 1 insertions, 1 deletions

diff --git a/src/seq.c b/src/seq.c
index 8fced4a0e..1124358cf 100644
--- a/src/seq.c
+++ b/src/seq.c
@@ -604,7 +604,7 @@ main (int argc, char **argv)
       if (asprintf (&s2, "%0.Lf", last.value) < 0)
         xalloc_die ();
 
-      if (seq_fast (s1, s2))
+      if (*s1 != '-' && *s2 != '-' && seq_fast (s1, s2))
         {
           IF_LINT (free (s1));
           IF_LINT (free (s2));