Problem parsing queries in verifypn

[Jiri Srba]

Try to verify the following query (-x 1) with the given pnml model.
(I include also the .xml file to be opened in the GUI).

It gives

Segmentation fault: 11

[Peter Gjøl Jensen (peter-gjoel)]

The bug is triggered by multiple subtractions in the same child in the query-xml.
We expected exactly two children for a <integer-difference>-expression -- the query-xml attached has three.

I have proposed a fix st. we parse expressions like

x - y -z

into pairwise form

(x - y) - z

with special case

- x

to

0 - x