Hi, I try to implement typed C-like structures in my little dsl. I was able to express structures using type-level naturals (type Ty is promoted):
> data Ty = TInt | TBool | TStruct Symbol [Ty] That allowed to implement all needed functions, including type-level function: > type family Get (n :: Nat) (xs :: [Ty]) :: Ty But it is not very convenient to identify struct's fields using naturals, and I wanted to change Ty definition to: > data Ty = TInt | TBool | TStruct Symbol [(Symbol, Ty)] It is much closer to how C-struct looks, but I was unable to implement required type function: > type family Find (s :: Symbol) (xs :: [(Symbol,Ty)]) :: Ty Which just finds a type in a associative list. Could someone give me a hint, how to do it? Or perhaps, is it just impossible thing to do? Thanks!
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