e4a3b434d7
@Kha The transition has begun :) I found and fixed a few bugs, but it is going well so far.
30 lines
700 B
Text
30 lines
700 B
Text
import Init.System.IO
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new_frontend
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structure MyState :=
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(bs : Nat := 0) -- backtrackable state
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(ps : Nat := 0) -- non backtrackable state
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instance : HasRepr MyState :=
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⟨fun s => repr (s.bs, s.ps)⟩
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instance : EStateM.Backtrackable Nat MyState :=
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{ save := fun s => s.bs,
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restore := fun s d => { s with bs := d } }
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abbrev M := EStateM String MyState
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def bInc : M Unit := -- increment backtrackble counter
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modify $ fun s => { s with bs := s.bs + 1 }
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def pInc : M Unit := -- increment nonbacktrackable counter
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modify $ fun s => { s with ps := s.ps + 1 }
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def tst : M MyState :=
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do bInc;
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pInc;
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((bInc *> throw "failed") <|> pInc);
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pInc;
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get
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#eval tst.run' {} -- (some (1, 3))
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