A question about the "awkward squad"

[Simon Peyton-Jones]

| > and is it (still?) true that GHC never expands them?
| 
| I'm not sure if GHC guarantees never to duplicate a redex, Simon PJ
| might know.

Yes, it's very careful not to duplicate a redex, except for ones of
known bounded size, like x +# y, where sharing the work costs more than
duplicating int.

But I'd advise against relying on this guarantee, because it's a
pragmatic one rather than a semantic one. 

Simon