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Diffstat (limited to 'src/Data/Fin/Strong.idr')
-rw-r--r-- | src/Data/Fin/Strong.idr | 124 |
1 files changed, 0 insertions, 124 deletions
diff --git a/src/Data/Fin/Strong.idr b/src/Data/Fin/Strong.idr deleted file mode 100644 index 1fcd667..0000000 --- a/src/Data/Fin/Strong.idr +++ /dev/null @@ -1,124 +0,0 @@ -module Data.Fin.Strong - -import Data.Fin -import Decidable.Equality.Core -import Syntax.PreorderReasoning - --- Definition ------------------------------------------------------------------ - -public export -data SFin : Nat -> Type where - FZ : SFin (S n) - FS : SFin (S n) -> SFin (S (S n)) - --- Properties - -export -Injective (FS {n}) where - injective Refl = Refl - -export -Uninhabited (SFin 0) where uninhabited x impossible - -export -Uninhabited (Strong.FS x = FZ) where uninhabited prf impossible - --- Conversion ------------------------------------------------------------------ - --- Utlities - -public export -0 indexPred : (0 x : Fin n) -> Nat -indexPred {n = S n} x = n - -public export -0 indexPredPrf : (0 x : Fin n) -> n = S (indexPred x) -indexPredPrf {n = S n} x = Refl - -public export -0 indexPred' : (0 x : SFin n) -> Nat -indexPred' {n = S n} x = n - -public export -0 indexPred'Prf : (0 x : SFin n) -> n = S (indexPred' x) -indexPred'Prf {n = S n} x = Refl - -public export -finToStrong : Fin n -> SFin n -finToStrong FZ = FZ -finToStrong (FS x) = - rewrite indexPredPrf x in - FS (replace {p = SFin} (indexPredPrf x) (finToStrong x)) - -public export -strongToFin : SFin n -> Fin n -strongToFin FZ = FZ -strongToFin (FS x) = FS (strongToFin x) - --- Properties - -export -finToStrongToFin : (x : Fin n) -> strongToFin (finToStrong x) = x -finToStrongToFin FZ = Refl -finToStrongToFin (FS FZ) = Refl -finToStrongToFin (FS (FS x)) = cong FS $ finToStrongToFin (FS x) - -export -strongToFinToStrong : (x : SFin n) -> finToStrong (strongToFin x) = x -strongToFinToStrong FZ = Refl -strongToFinToStrong (FS x) = cong FS (strongToFinToStrong x) - -export -Injective (strongToFin {n}) where - injective {x, y} prf = Calc $ - |~ x - ~~ finToStrong (strongToFin x) ..<(strongToFinToStrong x) - ~~ finToStrong (strongToFin y) ...(cong finToStrong prf) - ~~ y ...(strongToFinToStrong y) - --- Decidable Equality ---------------------------------------------------------- - -export -DecEq (SFin n) where - decEq x y = viaEquivalence - (MkEquivalence (injective {f = strongToFin}) (\prf => cong strongToFin prf)) - (decEq (strongToFin x) (strongToFin y)) - --- Useful Constructor ---------------------------------------------------------- - -%inline -export -FS' : SFin n -> SFin (S n) -FS' = finToStrong . FS . strongToFin - -export -Injective (FS' {n}) where - injective {x = FZ, y = FZ} prf = Refl - injective {x = FS x, y = FS y} prf = cong FS $ injective {f = FS'} $ injective prf - -export -sucNonZero : (x : SFin n) -> Not (FS' x = FZ) -sucNonZero FZ prf = absurd prf -sucNonZero (FS x) prf = absurd prf - -export -sucIsFS : (x : SFin (S n)) -> FS' x = FS x -sucIsFS x = rewrite strongToFinToStrong x in Refl - --- Num Interface --------------------------------------------------------------- - -public export -{n : Nat} -> Num (SFin (S n)) where - x + y = finToStrong (strongToFin x + strongToFin y) - x * y = finToStrong (strongToFin x * strongToFin y) - fromInteger = finToStrong . restrict n - --- Weaken and Shift ------------------------------------------------------------ - -export -weakenN : (0 k : Nat) -> SFin n -> SFin (n + k) -weakenN k = finToStrong . weakenN k . strongToFin - -export -shift : (k : Nat) -> SFin n -> SFin (k + n) -shift k = finToStrong . shift k . strongToFin |