The following code should require that the student enter "-1 7/10", but this generates an error message "You can only use '-' with (non-negative) numbers"

Any thoughts?

Adam

----

DOCUMENT();

loadMacros(

"PGstandard.pl", # Standard macros for PG language

"MathObjects.pl",

"contextFraction.pl",

);

$a1 = -17;

$a2 = 10;

Context("LimitedFraction");

$ansa = Compute("$a1/$a2");

Context()->texStrings;

BEGIN_TEXT

\( \frac{$a1}{$a2}= \) \{ans_rule(35) \} $BR$BR

END_TEXT

Context()->normalStrings;

ANS(Compute($ansa)->cmp);

ENDDOCUMENT();

Incidentally, there are two improvements I'd recommend for your code snippet above. First, you don't need the `Compute()`

in the `ANS`

call, as `$ansa`

is already a MathObject, so computing it again is a waste of time.

Second, you can use `$ansa`

to generate the fraction in the text of the problem rather than having to write the LaTeX yourself, but you have to force it to use `showMixedNumbers=>0`

to get it to show as a pure fraction:

```
\(\{$ansa->with(showProperFractions=>0)\} =\) \{ans_rule(35)\}
```

That way you don't have to have the same fraction twice and run the risk of getting the two instances out of synchronization when you change the definition of `$ansa`

later. :-)
Davide