** Using WeBWorK **

Here's a minimal example that shows a problem with perl's keys function within WW. When you open the following problem you will find that every time you hit "Check Answers" the elements in the list @vertKeys change order.

This has an easy workaround: add lex_sort to the definition of @vertKeys.

I take it this happens because even though the seed for the problem remains constant, the action of the keys function depends on other random factors that can't be controlled. But this behavior is counterintuitive; maybe the workaround should be incorpated into the WW base to produce a PGkeys command?

DOCUMENT();

loadMacros("PGstandard.pl",
"PGML.pl",
);

TEXT(&beginproblem);

%vertices = (
I => [10,30], J => [20,30], K => [30,30], L => [40,30],
E => [10,20], F => [20,20], G => [30,20], H => [40,20],
A => [10,10], B => [20,10], C => [30,10], D => [40,10] );
@vertKeys = keys( %vertices );



BEGIN_PGML

[@ join( ",", @vertKeys ) @]

END_PGML


ENDDOCUMENT();