BUG: gh-2935, fix printing of scalar float -0.0.

The issue was that the string value of scalar floating types equal to -0.0
lacked a trailing ".0".

    >>> print np.float64(-0.0)
    -0

The problem resulted from using val < 0 to check for a leading negative
sign. That expression evaluates false when val = -0.0, and the need to
append ".0" was not detected.

1 files changed, 1 insertions, 1 deletions

diff --git a/numpy/core/src/multiarray/scalartypes.c.src b/numpy/core/src/multiarray/scalartypes.c.src
index dacb9c9ce..52d59f43a 100644
--- a/numpy/core/src/multiarray/scalartypes.c.src
+++ b/numpy/core/src/multiarray/scalartypes.c.src
@@ -468,7 +468,7 @@ format_@name@(char *buf, size_t buflen, @type@ val, unsigned int prec)
 
     /* If nothing but digits after sign, append ".0" */
     cnt = strlen(buf);
-    for (i = (val < 0) ? 1 : 0; i < cnt; ++i) {
+    for (i = (buf[0] == '-') ? 1 : 0; i < cnt; ++i) {
         if (!isdigit(Py_CHARMASK(buf[i]))) {
             break;
         }