frenetic-lang/frenetic — pull request #292 by bcuccioli (2014-04-21 18:39:36+00:00)
Title: Fix Pattern diff.

`Pattern.diff` was not right. This fixes a bug in the fallthrough elimination optimization as witnessed by the following NetKAT program:

```
(filter not (ethTyp = 0x5ff); filter port = 1) |
(filter ethTyp = 0x806; port := 2)
```

@jnfoster let me know if this looks like it makes sense.