get sign of float helper as -1, +1 and 0

* add clarification for zero input

docs/source/util.rst

@@ -13,6 +13,7 @@ Table of contents (click to go):
 Functions:
 
 1. :c:func:`glm_sign`
+#. :c:func:`glm_signf`
 #. :c:func:`glm_rad`
 #. :c:func:`glm_deg`
 #. :c:func:`glm_make_rad`
@@ -27,7 +28,9 @@ Functions documentation
 
 .. c:function:: int  glm_sign(int val)
 
-    | returns sign of 32 bit integer as +1 or -1
+    | returns sign of 32 bit integer as +1, -1, 0
+
+    | **Important**: It returns 0 for zero input
 
     Parameters:
       | *[in]*  **val**   an integer
@@ -35,6 +38,18 @@ Functions documentation
     Returns:
       sign of given number
 
+.. c:function:: float  glm_signf(float val)
+
+    | returns sign of 32 bit integer as +1.0, -1.0, 0.0
+
+    | **Important**: It returns 0.0f for zero input
+
+    Parameters:
+      | *[in]*  **val**   a float
+
+    Returns:
+      sign of given number
+
 .. c:function:: float  glm_rad(float deg)
 
     | convert degree to radians

include/cglm/util.h

@@ -21,7 +21,9 @@
 #include "common.h"
 
 /*!
- * @brief get sign of 32 bit integer as +1 or -1
+ * @brief get sign of 32 bit integer as +1, -1, 0
+ *
+ * Important: It returns 0 for zero input
  *
  * @param val integer value
  */
@@ -31,6 +33,19 @@ glm_sign(int val) {
   return ((val >> 31) - (-val >> 31));
 }
 
+/*!
+ * @brief get sign of 32 bit float as +1, -1, 0
+ *
+ * Important: It returns 0 for zero/NaN input
+ *
+ * @param val float value
+ */
+CGLM_INLINE
+float
+glm_signf(float val) {
+  return (val > 0.0f) - (val < 0.0f);
+}
+
 /*!
  * @brief convert degree to radians
  *