quox/lib/Quox/Syntax/Qty/Three.idr

module Quox.Syntax.Qty.Three

import Quox.Pretty
import public Quox.Syntax.Qty
import Derive.Prelude

%default total
%language ElabReflection


public export
data Three = Zero | One | Any
%name Three pi, rh

%runElab derive "Three" [Eq, Ord, Show]


export
PrettyHL Three where
  prettyM pi = hl Qty <$>
    case pi of
      Zero => pure "0"
      One  => pure "1"
      Any  => ifUnicode "ω" "#"

public export
DecEq Three where
  decEq Zero Zero = Yes Refl
  decEq Zero One  = No $ \case _ impossible
  decEq Zero Any  = No $ \case _ impossible
  decEq One  Zero = No $ \case _ impossible
  decEq One  One  = Yes Refl
  decEq One  Any  = No $ \case _ impossible
  decEq Any  Zero = No $ \case _ impossible
  decEq Any  One  = No $ \case _ impossible
  decEq Any  Any  = Yes Refl


public export
plus : Three -> Three -> Three
plus Zero rh   = rh
plus pi   Zero = pi
plus _    _    = Any

public export
times : Three -> Three -> Three
times Zero _    = Zero
times _    Zero = Zero
times One  rh   = rh
times pi   One  = pi
times Any  Any  = Any

public export
lub3 : Three -> Three -> Maybe Three
lub3 p q =
  if p == Any || q == Any then Just Any
  else if p == q then Just p
  else Nothing

public export
data Compat3 : Rel Three where
  CmpRefl : Compat3 rh rh
  CmpAny  : Compat3 rh Any

public export
compat3 : Dec2 Compat3
compat3 pi rh with (decEq pi rh) | (decEq rh Any)
  compat3 pi pi  | Yes Refl | _        = Yes CmpRefl
  compat3 pi Any | No  _    | Yes Refl = Yes CmpAny
  compat3 pi rh  | No  ne   | No  na   =
    No $ \case CmpRefl => ne Refl; CmpAny => na Refl


public export
data IsSubj3 : Pred Three where
  SZero : IsSubj3 Zero
  SOne  : IsSubj3 One

public export
isSubj3 : Dec1 IsSubj3
isSubj3 Zero = Yes SZero
isSubj3 One  = Yes SOne
isSubj3 Any  = No $ \case _ impossible

public export
timesSubj3 : forall pi, rh. IsSubj3 pi -> IsSubj3 rh -> IsSubj3 (times pi rh)
timesSubj3 SZero SZero = SZero
timesSubj3 SZero SOne  = SZero
timesSubj3 SOne  SZero = SZero
timesSubj3 SOne  SOne  = SOne


public export
data IsGlobal3 : Pred Three where
  GZero : IsGlobal3 Zero
  GAny  : IsGlobal3 Any

public export
isGlobal3 : Dec1 IsGlobal3
isGlobal3 Zero = Yes GZero
isGlobal3 One  = No $ \case _ impossible
isGlobal3 Any  = Yes GAny


public export
IsQty Three where
  zero = Zero
  one  = One

  (+) = plus
  (*) = times

  lub = lub3

  IsZero     = Equal Zero
  isZero     = decEq Zero
  zeroIsZero = Refl

  Compat = Compat3
  compat = compat3

  IsSubj     = IsSubj3
  isSubj     = isSubj3
  zeroIsSubj = \Refl => SZero
  oneIsSubj  = SOne
  timesSubj  = timesSubj3

  IsGlobal     = IsGlobal3
  isGlobal     = isGlobal3
  zeroIsGlobal = \Refl => GZero

  prettySuffix = pretty0M


export Uninhabited (IsGlobal3 One) where uninhabited _ impossible

export Uninhabited (IsSubj3 Any) where uninhabited _ impossible