Information messages (not errors) from routines in the Calculus1 package are produced using the Maple userinfo mechanism, as level 1 messages.  However, userinfo messages cannot be caught by programs.  To make these messages available to programs that call Calculus1 routines, the message body (and some additional information when relevant) is stored in an internal variable.  To obtain the value of this variable, which is the most recent message produced, use the GetMessage() command.

$\mathrm{with}\left(\mathrm{Student}\left[\mathrm{Calculus1}\right]\right)\:$

$\mathrm{infolevel}\left[\mathrm{Student}\left[\mathrm{Calculus1}\right]\right]≔1\:$

$\mathrm{Diff}\left(x^2+x\,x\right)$

$\frac{\ⅆ}{\ⅆx}\left(x^2+x\right)$

$\mathrm{Rule}\left[\mathrm{`*`}\right]\left(\right)$

Creating problem #1

Rule [product] does not apply

$\frac{\ⅆ}{\ⅆx}\left(x^2+x\right)=\frac{\ⅆ}{\ⅆx}\left(x^2+x\right)$

$\mathrm{GetMessage}\left(\right)$

$''Rule\; [product]\; does\; not\; apply'',\mathrm{Diff},\left[\mathrm{product}\right]$