module Plutarch.Docs.PEqAndPOrd (PMaybe'(..)) where 

import Plutarch.Prelude

PEq & POrd

Plutarch level equality is provided by the PEq typeclass:

class PEq t where
  (#==) :: Term s t -> Term s t -> Term s PBool

PInteger implements PEq as you would expect. So you could do:

1 #== 2

That would yield a Term s PBool, which you would probably use with pif (or similar).

Similarly, PPartialOrd (and POrd) emulates Ord: (where PPartialOrd represents partial orders and POrd represents total orders)

class PEq => PPartialOrd t where
  (#<) :: Term s t -> Term s t -> Term s PBool
  (#<=) :: Term s t -> Term s t -> Term s PBool

class PPartialOrd => POrd t

It works as you would expect:

pif (1 #< 7) "indeed" "what"

evaluates to "indeed" - of type Term s PString.

For scott encoded types, you can easily derive PEq via generic deriving:

data PMaybe' a s
  = PNothing'
  | PJust' (Term s a)
  deriving stock Generic
  deriving anyclass (PlutusType, PEq)
instance DerivePlutusType (PMaybe' a) where type DPTStrat _ = PlutusTypeScott

For data encoded types, you can derive PEq, PPartialOrd and POrd via there data representation:

newtype PTriplet a s
  = PTriplet
      ( Term
          s
          ( PDataRecord
              '[ "x" ':= a
               , "y" ':= a
               , "z" ':= a
               ]
          )
      )
  deriving stock Generic
  deriving anyclass (PlutusType, PEq, PPartialOrd)

instance DerivePlutusType (PTriplet a) where type DPTStrat _ = PlutusTypeData

Aside: PEq derivation for data encoded types uses “Data equality”. It simply ensures the structure (as represented through data encoding) of both values are exactly the same. It does not take into account any custom PEq instances for the individual fields within.