Why do I get an error on

\starttext
\showmathfontcharacters
\stoptext

When that macro is defined in s-mat-10.mkiv as
\unexpanded\def\showmathfontcharacters
  {\dodoubleempty\doshowmathfontcharacters}


ConTeXt  ver: 2013.04.16 12:08 MKIV beta  fmt: 2013.4.19  int: english/english
! Undefined control sequence.
9 >>  \showmathfontcharacters

Hans van der Meer