39 lines
923 B
Text
39 lines
923 B
Text
inductive bvar : Type
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| mk (n : Nat)
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def bvar_eq : bvar → bvar → Bool
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| bvar.mk n1, bvar.mk n2 => n1=n2
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inductive bExpr : Type
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| BLit (b: Bool)
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| BVar (v: bvar)
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def benv := bvar → Bool
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def bEval : bExpr → benv → Bool
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| bExpr.BLit b, i => b
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| bExpr.BVar v, i => i v
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def init_benv : benv := λ v => false
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def update_benv : benv → bvar → Bool → benv
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| i, v, b => λ v2 => if (bvar_eq v v2) then b else (i v2)
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inductive bCmd : Type
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| bAssm (v : bvar) (e : bExpr)
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| bSeq (c1 c2 : bCmd)
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-- Unlike Lean 3, we can have nested match-expressions and still use structural recursion
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def cEval : benv → bCmd → benv
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| i0, c => match c with
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| bCmd.bAssm v e => update_benv i0 v (bEval e i0)
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| bCmd.bSeq c1 c2 =>
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let i1 := cEval i0 c1
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cEval i1 c2
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def myFirstProg := bCmd.bAssm (bvar.mk 0) (bExpr.BLit false)
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def newEnv :=
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cEval init_benv myFirstProg
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#eval newEnv (bvar.mk 0)
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