Add Plutus example that computes sum [1..n]

plutus-example/plutus-example/app/plutus-example.hs

@@ -10,7 +10,7 @@ import           Cardano.PlutusExample.CustomDatumRedeemerGuess
 import           Cardano.PlutusExample.AlwaysSucceeds (alwaysSucceedsScript)
 import           Cardano.PlutusExample.DatumRedeemerGuess (guessScript)
 import           Cardano.PlutusExample.MintingScript (apiExamplePlutusMintingScript)
-
+import           Cardano.PlutusExample.Sum (sumScript)
 
 main :: IO ()
 main = do
@@ -21,4 +21,5 @@ main = do
   _ <- writeFileTextEnvelope (dir </> "guess-42-datum-42-txin.plutus") Nothing guessScript
   _ <- writeFileTextEnvelope (dir </> "custom-guess-42-datum-42.plutus") Nothing customGuessScript
   _ <- writeFileTextEnvelope (dir </> "anyone-can-mint.plutus") Nothing apiExamplePlutusMintingScript
+  _ <- writeFileTextEnvelope (dir </> "sum.plutus") Nothing sumScript
   return ()

plutus-example/plutus-example/plutus-example.cabal

@@ -49,7 +49,7 @@ library
                         Cardano.PlutusExample.DatumRedeemerGuess
                         Cardano.PlutusExample.MintingScript
                         Cardano.PlutusExample.CustomDatumRedeemerGuess
-
+                        Cardano.PlutusExample.Sum
   build-depends:        bytestring
                       , cardano-api
                       , plutus-ledger

plutus-example/plutus-example/src/Cardano/PlutusExample/Sum.hs

@@ -0,0 +1,68 @@
+{-# LANGUAGE BangPatterns #-}
+{-# LANGUAGE DataKinds #-}
+{-# LANGUAGE FlexibleContexts #-}
+{-# LANGUAGE NoImplicitPrelude #-}
+{-# LANGUAGE ScopedTypeVariables #-}
+{-# LANGUAGE TemplateHaskell #-}
+{-# LANGUAGE TypeApplications #-}
+{-# LANGUAGE TypeFamilies #-}
+{-# LANGUAGE TypeOperators #-}
+
+module Cardano.PlutusExample.Sum
+  where
+
+import           Prelude hiding (($),(==),(+),(-))
+
+import           Cardano.Api.Shelley (PlutusScript (..), PlutusScriptV1)
+
+import           Codec.Serialise
+import qualified Data.ByteString.Lazy as LBS
+import qualified Data.ByteString.Short as SBS
+
+import qualified Ledger.Typed.Scripts as Scripts
+import qualified Plutus.V1.Ledger.Scripts as Plutus
+import           PlutusTx (Data (..))
+import qualified PlutusTx
+import           PlutusTx.Prelude hiding (Semigroup (..), unless)
+
+
+smartSum :: Integer -> Integer
+smartSum a = loop a 0
+ where
+  loop !n !acc = if n==0
+    then acc
+    else loop (n - 1) (n + acc)
+
+-- | The validation function (DataValue -> RedeemerValue -> ScriptContext -> Bool)
+{-# INLINABLE validateSum #-}
+validateSum :: Integer -> Integer -> x -> Bool
+validateSum n s _ = isGoodSum n s
+
+{-# INLINABLE isGoodSum #-}
+isGoodSum :: Integer -> Integer -> Bool
+isGoodSum n s = smartSum n == s
+
+
+data SmartSum
+instance Scripts.ValidatorTypes SmartSum where
+    type instance RedeemerType SmartSum = Integer
+    type instance DatumType SmartSum = Integer
+
+sumInstance :: Scripts.TypedValidator SmartSum
+sumInstance = Scripts.mkTypedValidator @SmartSum
+    $$(PlutusTx.compile [|| validateSum ||])
+    $$(PlutusTx.compile [|| wrap ||])
+      where
+        wrap = Scripts.wrapValidator @Integer @Integer
+
+validator :: Plutus.Validator
+validator = Scripts.validatorScript sumInstance
+
+script :: Plutus.Script
+script = Plutus.unValidatorScript validator
+
+sumScriptShortBs :: SBS.ShortByteString
+sumScriptShortBs = SBS.toShort . LBS.toStrict $ serialise script
+
+sumScript :: PlutusScript PlutusScriptV1
+sumScript = PlutusScriptSerialised sumScriptShortBs