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25 lines
697 B
Idris
25 lines
697 B
Idris
myReplace : forall p . (0 rule : x = y) -> (1 val : p y) -> p x
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myReplace Refl prf = prf
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bad : (0 x : Bool) -> Bool
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bad False = True
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bad True = False
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data LT : Nat -> Nat -> Type where
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LeZ : LT Z (S k)
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LeS : LT j k -> LT (S j) (S k)
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-- prf isn't used in the run time case tree, so erasure okay
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minus : (x : Nat) -> (y : Nat) -> (0 prf : LT y x) -> Nat
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minus (S k) Z LeZ = S k
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minus (S k) (S j) (LeS p) = minus k j p
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-- y is used in the run time case tree, so erasure not okay
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minusBad : (x : Nat) -> (0 y : Nat) -> (0 prf : LT y x) -> Nat
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minusBad (S k) Z LeZ = S k
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minusBad (S k) (S j) (LeS p) = minusBad k j p
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prf : {k : _} -> LT k (S (S k))
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prf {k=Z} = LeZ
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prf {k=S _} = LeS prf
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