Pierre-Etienne Moreau mentioned anti-pattern matching in his talk about TOM at the SUD. The feature is simple and easy to understand (almost obvious). Anti-pattern matching would be a nice feature to have in Stratego.

Example:
———————————————————————————-
AddBlock :
If(e, stm1, stm2) -> If(e, Block([stm1]), stm2)
where
<not(?Block(_))> stm2
———————————————————————————-

It would be nice to be able to express this not concisely in the pattern. Currently, it is already possible to do this:

---

AddBlock :
If(e, <not(?Block(_)); ?stm1>, stm2) -> If(e, Block([stm1]), stm2)
———————————————————————————-

but this is a bit of a hack.

Something like this would be cleaner:

---

AddBlock :
If(e, stm1@not(Block(_)), stm2) -> If(e, Block([stm1]), stm2)
———————————————————————————-

where not( ) is a new kind of pattern added to the language

without variable binding it would look like:

---

AddBlock :
If(e, not(Block(_)), stm2) -> If(e, Block([stm1]), stm2)
———————————————————————————-

not is already a reserved keyword in Stratego.

Submitted on 2 December 2006 at 23:08