## Forum archive 2000-2006

### Carl F. Letsche - Using submitted values within a problem

by Arnold Pizer -
Number of replies: 0
 Using submitted values within a problem topic started 10/18/2001; 1:50:51 PMlast post 10/25/2001; 3:50:17 PM
 Carl F. Letsche - Using submitted values within a problem  10/18/2001; 1:50:51 PM (reads: 1050, responses: 3) Under an *old* version of WeBWorK, I unknowingly exploited what was apparently a bug that's since been fixed. I'm wondering how to do it with the new system. I'll describe what I did, and include the old problem at the end, for analysis. Basically, I grabbed the strings submitted in the answer slot on the web page, then used 'eval' to make the strings into numerical values that were then used in the problem to compute whether the pair of answers were correct - each answer depended on the other (the objective was to find values for a and r so that the geometric series a*r^n converged to a random value). How can i do this now? I tried tapping into the answer hash, but it's non-existant until the answer evaluator runs, and the answer evaluator needs the values... Here's the original problem; (just trying to make it readable!) ##Description##KEYWORDS('series', 'geometric')##Find a geometric series converging to a given value##enddescriptionloadMacros( PG.pl, PGbasicmacros.pl, PGchoicemacros.pl, PGanswermacros.pl );$showPartialCorrectAnswers = 1;&DOCUMENT; TEXT(&beginproblem);$b = non_zero_random(-20,20);TEXT(EV2(<= 1)) { &ANS(std_num_cmp_list(.01,"",$b*(1-($r)),0));} else { if ($r==0) { &ANS(std_num_cmp_list(.01,"",$b*(1-($r)),1)); } else { &ANS(std_num_cmp_list(.01,"",$b*(1-($r)),1-($a/$b))); } }&ENDDOCUMENT <| Post or View Comments |>  Gavin LaRose - Re: Using submitted values within a problem 10/19/2001; 8:08:00 AM (reads: 1281, responses: 0) This sounds like something Zig addressed in a previous thread: http://webhost.math.rochester.edu/webworkdocs/discuss/msgReader$422 might be helpful. If not, I'm sure someone will come up with a better answer... Gavin <| Post or View Comments |>

 Zbigniew Fiedorowicz - Re: Using submitted values within a problem  10/19/2001; 9:47:22 AM (reads: 1260, responses: 1) There was a followup discussion on the same topic in another thread: Zig <| Post or View Comments |>

 Bill Ziemer - Re: Using submitted values within a problem  10/25/2001; 3:50:17 PM (reads: 1466, responses: 0) The error "use of uninitialized string..." will appear, and precreation will complain as well since variables of the form $inputs_ref->{first_answer}; haven't been set by the webserver yet. Simple fix, put:$inputs_ref->{first_answer}='' unless defined \$inputs_ref->{first_answer}; in the pg file. <| Post or View Comments |>