Inhibitor and Outgoing Arcs

[vanrein]

The same place may point to a transition with both an inhibitor arc and an outgoing arc. This can be meaningful when the outgoing arc has a lower multiplicity than the inhibitor.

Semantics for 1.1 will be made to blocks this until well-defined, and prior versions always block inhibitors with multiplicity.

The approach may require (in the general case) a split of a place into two identical copies, except:

• one handles outgoing arcs, the other handles inhibitors
• this leads to separate checks for the two constraints: having enough, but not too much
• the split is not needed if the same (p,t) pair does not combine these two constrints
• the split might be avoided for other corner cases that coincide with bit masks... but that is perhaps odd
• to keep the inhibitor-processing place clone up to date, use a negative addend (the other place ensures the outcome is positive)
• note how added and subber now both use signed bit fields