81 lines
1.9 KiB
Idris
81 lines
1.9 KiB
Idris
module Quox.Thin.Base
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import Data.Fin
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import Data.DPair
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%default total
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||| "order preserving embeddings", for recording a correspondence between a
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||| smaller scope and part of a larger one. the third argument is a bitmask
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||| representing this OPE, unique for a given `n`.
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public export
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data OPE : (m, n, mask : Nat) -> Type where
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[search m n]
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Stop : OPE 0 0 0
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Drop : OPE m n mask -> mask' = mask + mask -> OPE m (S n) mask'
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Keep : OPE m n mask -> mask' = (S (mask + mask)) -> OPE (S m) (S n) mask'
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%name OPE ope
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export
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Show (OPE m n mask) where
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showPrec d Stop = "Stop"
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showPrec d (Drop ope Refl) = showCon d "Drop" $ showArg ope ++ " Refl"
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showPrec d (Keep ope Refl) = showCon d "Keep" $ showArg ope ++ " Refl"
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public export %inline
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drop : OPE m n mask -> OPE m (S n) (mask + mask)
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drop ope = Drop ope Refl
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public export %inline
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keep : OPE m n mask -> OPE (S m) (S n) (S (mask + mask))
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keep ope = Keep ope Refl
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public export
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data IsStop : OPE m n mask -> Type where ItIsStop : IsStop Stop
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public export
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data IsDrop : OPE m n mask -> Type where ItIsDrop : IsDrop (Drop ope eq)
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public export
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data IsKeep : OPE m n mask -> Type where ItIsKeep : IsKeep (Keep ope eq)
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export
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0 zeroIsStop : (ope : OPE m 0 mask) -> IsStop ope
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zeroIsStop Stop = ItIsStop
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||| everything selected
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public export
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id : {m : Nat} -> Subset Nat (OPE m m)
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id {m = 0} = Element _ Stop
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id {m = S m} = Element _ $ Keep id.snd Refl
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public export %inline
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0 id' : OPE m m Base.id.fst
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id' = id.snd
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||| nothing selected
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public export
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zero : {m : Nat} -> OPE 0 m 0
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zero {m = 0} = Stop
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zero {m = S m} = Drop zero Refl
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||| a single slot selected
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public export
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one : Fin n -> Subset Nat (OPE 1 n)
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one FZ = Element _ $ keep zero
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one (FS i) = Element _ $ drop (one i).snd
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public export %inline
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0 one' : (i : Fin n) -> OPE 1 n (one i).fst
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one' i = (one i).snd
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public export
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record SomeOPE n where
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constructor MkOPE
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{mask : Nat}
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0 ope : OPE m n mask
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