[LON-CAPA-users] formula response question

James Mueller lon-capa-users@mail.lon-capa.org
Sat, 21 Feb 2009 21:05:12 -0500


A student in a calculus course is entering an answer to a formula  
response problem and keeps getting "Unable to understand formula" even  
when they enter something simple like "x" for their answer.  The rest  
of the students are reported to be not having troubles.  I assumed it  
must be some problem with the script tat was triggered by the numbers  
used for this particular problem.  After a quick look, I can't see  
anything, but I have to admit my perl is rusty.  Anybody else se  
anything?

The script is

<problem>
<meta name="isbasedontime" content="1235265561" />
<meta name="isbasedonres" content="\%2fres\%2fpitt\%2fathanas\%2fc2\ 
%2ddiffeq\%2d21\%2eproblem" />
     <script type="loncapa/perl">
$b=0; $d=0; while($b==0 || $d==0){$b=&random(-10,10,1); 
$d=&random(-10,10,1);}
$a=-1*$b/$d; while($a==-1*$b/$d){$a=&random(1,10,1);}
$c=&random(1,10,1); $i=&random(1,50,1);
if($b<0){$s=" ";} if($b>0){$s="+";}
$M1=$c/($a*$d+$b); $M2=$i-$M1;
$solution="$M1*exp($d*x)+$M2*exp(-1*$b/$a*x) ";
  </script>
  <startouttext />
<br />
Determine the solution to the initial value differential equation <m  
eval="on"> \[  $a y' $s $b y = $c e^{$d x} \hspace{.2in} y ( 0 )= $i  
\]</m>
<endouttext />

<p />
<startouttext /><m>$ y ( x ) =  $</m><endouttext />
<formularesponse samples="x@1:3#4" answer="$solution" id="11">
<responseparam name="tol" default="0.001" type="tolerance"  
description="Numerical Tolerance" />
         <textline readonly="no" size="35" />
     </formularesponse>
</problem>

And the students variables for this problem are

%! 
=(E2BIG=>0,EACCES=>0,EADDRINUSE=>0,EADDRNOTAVAIL=>0,EADV=>0,EAFNOSUPPORT 
=>0,EAGAIN=>0,EALREADY=>0,EBADE=>0,EBADF=>0,EBADFD=>0,EBADMSG=>0,EBADR=> 
0,EBADRQC=>0,EBADSLT=>0,EBFONT=>0,EBUSY=>0,ECANCELED=>0,ECHILD=>0,ECHRNG 
=>0,ECOMM=>0,ECONNABORTED=>0,ECONNREFUSED=>0,ECONNRESET=>0,EDEADLK=>0,ED 
EADLOCK=>0,EDESTADDRREQ=>0,EDOM=>0,EDOTDOT=>0,EDQUOT=>0,EEXIST=>0,EFAULT 
=>0,EFBIG=>0,EHOSTDOWN=>0,EHOSTUNREACH=>0,EIDRM=>0,EILSEQ=>0,EINPROGRESS 
=>0,EINTR=>0,EINVAL=>0,EIO=>0,EISCONN=>0,EISDIR=>0,EISNAM=>0,EKEYEXPIRED 
=>0,EKEYREJECTED=>0,EKEYREVOKED=>0,EL2HLT=>0,EL2NSYNC=>0,EL3HLT=>0,EL3RS 
T=>0,ELIBACC=>0,ELIBBAD=>0,ELIBEXEC=>0,ELIBMAX=>0,ELIBSCN=>0,ELNRNG=>0,ELOOP=>0,EMEDIUMTYPE=>0,EMFILE=>0,EMLINK=>0,EMSGSIZE=>0,EMULTIHOP=>0,ENAMETOOLONG=>0,ENAVAIL=>0,ENETDOWN=>0,ENETRESET=>0,ENETUNREACH=>0,ENFILE=>0,ENOANO=>0,ENOBUFS=>0,ENOCSI=>0,ENODATA=>0,ENODEV=>0,ENOENT=>0,ENOEXEC=>0,ENOKEY=>0,ENOLCK=>0,ENOLINK=>0,ENOMEDIUM=>0,ENOMEM=>0,ENOMSG=>0,ENONET=>0,ENOPKG=>0,ENOPROTOOPT=>0,ENOSPC=>0,ENOSR=>0,ENOSTR=>0,ENOSYS=>0,ENOTBLK=>0,ENOTCONN=>0,ENOTDIR=>0,ENOTEMPTY=>0,ENOTNAM=>0,ENOTRECOVERABLE=>0,ENOTSOCK=>0,ENOTSUP=>0,ENOTTY=>0,ENOTUNIQ=>0,ENXIO=>0,EOPNOTSUPP=>0,EOVERFLOW=>0,EOWNERDEAD=>0,EPERM=>0,EPFNOSUPPORT=>0,EPIPE=>0,EPROTO=>0,EPROTONOSUPPORT=>0,EPROTOTYPE=>0,ERANGE=>0,EREMCHG=>0,EREMOTE=>0,EREMOTEIO=>0,ERESTART=>0,EROFS=>0,ESHUTDOWN=>0,ESOCKTNOSUPPORT=>0,ESPIPE=>0,ESRCH=>0,ESRMNT=>0,ESTALE=>0,ESTRPIPE=>0,ETIME=>0,ETIMEDOUT=>0,ETOOMANYREFS=>0,ETXTBSY=>0,EUCLEAN=>0,EUNATCH=>0,EUSERS=>0,EWOULDBLOCK=>0,EXDEV=>0,EXFULL=>0)
$M1=7
$M2=-2
$a=4
$b=-7
$c=7
$d=2
$deg2rad=0.0174532925199433
$i=5
$pi=3.14159265358979
$rad2deg=57.2957795130823
$s=
$solution=7*exp(2*x)+-2*exp(-1*-7/4*x)