[m-dev.] Typeclass constraints on types

[Ralph Becket]

I want to describe a type thus:

:- type show_pred == ( pred(X, io__state, io__state) <= showable(X) ).

But I can't do it: I get

Error: free type parameter in RHS of type definition

But X isn't really free, it's constrained.  So what's the trick?  

--
Ralph Becket      |      MSR Cambridge      |      rbeck at microsoft.com 
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