Using a type of a parameterized data type in a Haskell function -

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let's have algebraic data type in haskell:

data foo = ...

i'd have function "extract" type a , it, assuming satisfies conditions. specifically, need like:

fun :: bounded => foo ->

with intended usage follows:

fun foo = maxbound ::

of course notation incorrect in haskell, think intentions clear. possible this?

you don't need anything, works. 

fun :: bounded => foo -> fun _ = maxbound

the compiler knows result of fun a , therefore call correct maxbound.


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