provide signbit mapper for real values * mappers.cc (Fsignbit): New function and tests. * ov-base.cc (octave_base_value::get_umap_name): Include signbit in the list. * ov-base.h (octave_base_value::unary_mapper_t): Include umap_xsignbit in the list. * ov-float.cc (octave_float_scalar::map): Handle xsignbit. * ov-scalar.cc (octave_scalar::map): Handle xsignbit. * ov-re-mat.cc (octave_matrix::map): Handle xsignbit. * ov-flt-re-mat.cc (octave_float_matrix::map): Handle xsignbit. * lo-mappers.h (xsignbit): New template function. * arith.txi: Document signbit.

--- a/liboctave/numeric/lo-mappers.h
+++ b/liboctave/numeric/lo-mappers.h
@@ -401,4 +401,11 @@
   return retval;
 }
 
+template <typename T>
+T
+xsignbit (T x)
+{
+  return signbit (x);
+}
+
 #endif