/*i would like to put results of a function into a file for later gnuplotting it.
first step is to evaluate the function without quitting if an error occurs this is done with "try1d" - the result is either a value or "?".
second step is to put all the values (or the "?") into an arry. i need this step, because if i would try to put the values directly into a file using with_stdout, then all error messages appear in this file, too.
last step would be to put those values into a file.

i fail in doing second step. 
below you can see the function definitions and a test run. as you can see, maxima does not store the value inside the array i created via make_array, it does store a lisp expression. how can i force evaluation?
*/

/**********************************************************/
try1D(func1D, x) := block([result],
  result : ev( errcatch( func1D(x)), numer),
  if( length(result) < 1) then( "?") else (first(result)));



testfunc1d(func, xmin, xmax, xstep) := block([
  n : ev((xmax - xmin)/xstep, numer), x, result_array],
  print( "n = ", n),
  result_array : make_array( any, ?truncate( 2 * (n + 1))), 
  (for i: 0 thru n do (
    x : xmin + xstep * i,
    result_array[ 2 * i ] : x,
    result_array[ 2 * i + 1] : ev(try1D(func, x)))),
result_array);
/**********************************************************/

(%i72) testfunc1d(sin, 2.0, 9.0, 2.0);

n =  3.5 
(%o72) {Array:  #(2.0 (($try1D SIMP) %SIN 2.0) 4.0 (($try1D SIMP) %SIN 4.0) 6.#
0
  (($try1D SIMP) %SIN 6.0) 8.0 (($try1D SIMP) %SIN 8.0) NIL)}