function value = ch_is_digit ( c )

%*****************************************************************************80
%
% ch_is_digit() returns true if the character C is a digit.
%
%  Licensing:
%
%    This code is distributed under the MIT license.
%
%  Modified:
%
%    22 February 2010
%
%  Author:
%
%    John Burkardt
%
%  Input:
%
%    character C, a character.
%
%  Output:
%
%    integer VALUE: true if C is a digit, false otherwise.
%
  if ( '0' <= c && c <= '9' )
    value = true;
  else
    value = false;
  end

  return
end
