Ah, thanks. I think one needs (structural) type transformation for the flexibility I had mind, things like swapping sum operands, re-ordering concantenation ope

Ah, thanks. I think one needs (structural) type transformation for the flexibility I had mind, things like swapping sum operands, re-ordering concantenation operands. Uh... did you see my bug report on your webpage (first sentence above)? That link still doesn't work properly.