tolower/toupper functions return complex numbers unchanged (bug #52380). * mappers.cc (Ftolower, Ftoupper): Add BIST tests for new behavior. * ov-complex.cc (octave_complex::map): Directly return input for cases of umap_xtolower and umap_xtoupper. * ov-cx-mat.cc (octave_complex_matrix::map): Directly return input for cases of umap_xtolower and umap_xtoupper. * ov-flt-complex.cc (octave_float_complex::map): Directly return input for cases of umap_xtolower and umap_xtoupper. * ov-flt-cx-mat.cc (octave_float_complex_matrix::map): Directly return input for cases of umap_xtolower and umap_xtoupper.

--- a/libinterp/octave-value/ov-complex.cc	Thu Jan 11 20:30:08 2018 +0100
+++ b/libinterp/octave-value/ov-complex.cc	Wed Jan 10 17:50:13 2018 -0500
@@ -526,6 +526,11 @@
     SCALAR_MAPPER (isna, octave::math::isna);
     SCALAR_MAPPER (isnan, octave::math::isnan);
 
+    // Special cases for Matlab compatibility.
+    case umap_xtolower:
+    case umap_xtoupper:
+      return scalar;
+
     default:
       return octave_base_value::map (umap);
     }