use gnulib log2 modules (bug #42583) * bootstrap.conf (gnulib_modules): Include log2, log2f, log2-ieee, and log2f-ieee, in the list. * lo-mappers.cc (xlog2): Use gnulib:: versions of log2 and log2f. * CMatrix.cc, dMatrix.cc, fCMatrix.cc, fMatrix.cc: Use xlog2.

%!function r = f (x)
%!  if (ischar (x))
%!    r = x;
%!  else
%!    error ("expecting character string");
%!  endif
%!endfunction

%!assert (eval ("f 10;"), "10");