mirror of
https://github.com/idris-lang/Idris2.git
synced 2024-12-26 13:11:30 +03:00
33 lines
894 B
Idris
33 lines
894 B
Idris
data IsS : (Nat -> Nat) -> Type where
|
|
Indeed : (s : Nat -> Nat) -> s === S -> IsS s
|
|
|
|
------------------------------------------------------------------------
|
|
-- 1.
|
|
-- the S pattern is forced by the fact the parameter is instantiated
|
|
-- so everything is fine
|
|
|
|
-- either left implicit
|
|
indeed : IsS S -> S === S
|
|
indeed (Indeed _ eq) = eq
|
|
|
|
-- or made explicit
|
|
indeed2 : IsS S -> S === S
|
|
indeed2 (Indeed S eq) = eq
|
|
|
|
------------------------------------------------------------------------
|
|
-- 2. The S pattern is not forced by the parameter (a generic variable)
|
|
|
|
-- either don't match on it
|
|
indeed3 : IsS s -> s === S
|
|
indeed3 (Indeed s eq) = eq
|
|
|
|
-- or match on the proof that forces it
|
|
indeed4 : IsS s -> s === S
|
|
indeed4 (Indeed S Refl) = Refl
|
|
-- ^ forced by Refl
|
|
|
|
-- If you don't: too bad!
|
|
fail : IsS s -> s === S
|
|
fail (Indeed S eq) = eq
|
|
-- ^ not Refl, S not forced! OUCH
|