[LON-CAPA-users] Forcing students to submit valid expressions for formula responses.

[Gerd Kortemeyer]

Hi,

On Oct 21, 2013, at 10:23 AM, Angus Findlay <afindlay at mta.ca> wrote:

> When I give students formula response questions some of them don’t submit valid mathematic expressions. The most common problems are:
> 
> 1) Not having balanced brackets. (i.e. number of left brackets do not match number of right brackets)
> 2) Including invalid characters, such as quotation signs.
> 3) Not including brackets, when necessary. (eg. 2^-1/2 instead of 2^(-1/2))
> 
> I want to tell them that the expression is invalid, tell them why, and allow them to enter it again, without penalty. (Right now my LON-CAPA server times out on them, and asks them to try again later.)
> 
> Is there a piece of standard code I can use for this, or if not, what it the easiest to implement a solution to this?

You can use <customresponse> (available now) and intercept the answer before passing it on to the symbolic algebra system, or you can use the pre-processor before the formulas are passed on to the regular <mathresponse> or <formularesponse> - but I am not sure if the pre-process argument is in 2.10.1, and whether or not it will be in 2.11.

I have no prefabricated piece of code on hand. I continue to be puzzled by the students' inability to produce valid expressions - it seems like there are very few rules, and they presumably used those $@$!$# graphing calculators for years …

- Gerd.