Re: [WWdevel] parser fun_cmp() error?

[Davide P.C. <dp...@un...>]

> You can also adjust the tolerances.  The default relTol is .1 meaning 
> 0.1%.  This may not be suitable for this problem.

Yes, but my point was (as you suggest above) that that isn't really 
going to solve the problem because the two functions really ARE nearly 
identical on the tested range.  Jacking up the tolerances in order to 
distinguish between these two will cause it to fail to mark correct 
answers where the students have replaced the fractions by decimal 
approximations, for example.  This is why I said "yes and no" as the 
answer to "is this a tolerance issue".

This problem has got me thinking about whether it would be possible to 
help the professor out with analyzing their functions and telling them 
if they are nearly linear, for example, or if the values are very large 
or very small, or if the value of the function varies greatly if the 
constants are varied slightly, and other such things that could cause 
numeric instability.  It would be possible to set a flag that starts 
"testing mode" and have the answer checker report these sorts of 
potential problems.  Even just producing a graph of the function on the 
default range might be illuminating.  Do you think this might be 
helpful?

Davide