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add Var.tighten*

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rhiannon morris 2022-02-27 02:17:51 +01:00
parent ddba87262d
commit 362c9354cf
1 changed files with 21 additions and 0 deletions
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21
src/Quox/Syntax/Var.idr
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@ -263,3 +263,24 @@ decEqFromBool i j =
%transform "Var.decEq" varDecEq = decEqFromBool
public export %inline DecEq (Var n) where decEq = varDecEq
parameters {auto _ : Alternative f}
export
tighten : OPE m n -> Var n -> f (Var m)
tighten Id i = pure i
tighten (Drop q) VZ = empty
tighten (Drop q) (VS i) = tighten q i
tighten (Keep q) VZ = pure VZ
tighten (Keep q) (VS i) = VS <$> tighten q i
export
tightenInner : {n : Nat} -> m `LTE` n -> Var n -> f (Var m)
tightenInner = tighten . dropInner
export
tightenN : (m : Nat) -> Var (m + n) -> f (Var n)
tightenN m = tighten $ dropInnerN m
export
tighten1 : Var (S n) -> f (Var n)
tighten1 = tightenN 1