function truefalse = ch_is_digit ( c )

% CH_IS_DIGIT returns TRUE (1) if the character C is a digit.
%
%  Modified:
%
%    14 June 2003
%
%  Author:
%
%    John Burkardt
%
%  Parameters:
%
%    Input, character C, a character.
%
%    Output, integer TRUEFALSE, is 1 if C is a digit, 0 otherwise.
%
  if ( '0' <= c & c <= '9' )
    truefalse = 1;
  else
    truefalse = 0;
  end