function rv = erreval(error_prefix, try_str, catch_str)
  ## erreval() extends the built-in function eval().  Return 0 if
  ## try_str does not raise the error of type error_prefix, return 1
  ## otherwise.
  
  global unittest_results;
  for k = 1:length(unittest_results.eval_globals)
    eval(unittest_results.eval_globals{k});
  end
  
  rv = 0;
  try
    eval(try_str);
  catch
    rv = errcheck(error_prefix);
  end  
endfunction
