[Haskell-cafe] Cyclical Type Synonyms
tomahawkins at gmail.com
Thu Feb 16 08:52:14 EST 2006
I want to define a type for a function that returns its own type...
type F a = a -> (F a,a)
But the compiler gives me an error: "Cycle in type synonym declaration: ...".
Why is this a restriction?
Of course I can create a user defined type, but then I need an extra
mechanism to call the embedded function:
data F a = F (a -> (F a ,a))
call :: F a -> a -> (F a, a)
call (F f) a = f a
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