playground: More comments in sample contracts

* More comments
* Use `PendingTx'` where possible

plutus-playground/plutus-playground-server/usecases/CrowdFunding.hs

@@ -48,52 +48,66 @@ PlutusTx.makeLift ''CampaignAction
 contributionScript :: Campaign -> ValidatorScript
 contributionScript cmp  = ValidatorScript val where
     val = Ledger.applyScript mkValidator (Ledger.lifted cmp)
-    mkValidator = Ledger.fromCompiledCode $$(PlutusTx.compile [|| (\Campaign{..} (act :: CampaignAction) (con :: CampaignActor) (p :: PendingTx ValidatorHash) ->
-        let
-
-            infixr 3 &&
-            (&&) :: Bool -> Bool -> Bool
-            (&&) = $$(PlutusTx.and)
-
-            PendingTx ps outs _ _ (Height h) _ _ = p
-
-            deadline :: Int
-            deadline = let Height h' = campaignDeadline in h'
-
-            collectionDeadline :: Int
-            collectionDeadline = let Height h' = campaignCollectionDeadline in h'
-
-            target :: Int
-            target = let Value v = campaignTarget in v
-
-            -- | The total value of all contributions
-            totalInputs :: Int
-            totalInputs =
-                let v (PendingTxIn _ _ (Value vl)) = vl in
-                $$(P.foldr) (\i total -> total + v i) 0 ps
-
-            isValid = case act of
-                Refund -> -- the "refund" branch
-                    let
-
-                        contributorTxOut :: PendingTxOut -> Bool
-                        contributorTxOut o = case $$(pubKeyOutput) o of
-                            Nothing -> False
-                            Just pk -> $$(eqPubKey) pk con
-
-                        -- Check that all outputs are paid to the public key
-                        -- of the contributor (this key is provided as the data script `con`)
-                        contributorOnly = $$(P.all) contributorTxOut outs
-
-                        refundable = h > collectionDeadline && contributorOnly && $$(txSignedBy) p con
-
-                    in refundable
-                Collect -> -- the "successful campaign" branch
-                    let
-                        payToOwner = h > deadline && h <= collectionDeadline && totalInputs >= target && $$(txSignedBy) p campaignOwner
-                    in payToOwner
-        in
-        if isValid then () else $$(P.error) ()) ||])
+    mkValidator = Ledger.fromCompiledCode $$(PlutusTx.compile [|| 
+
+        -- The validator script is a function of for arguments:
+        -- 1. The 'Campaign' definition. This argument is provided by the Plutus client, using 'Ledger.applyScript'.
+        --    As a result, the 'Campaign' definition is part of the script address, and different campaigns have different addresses.
+        --    The Campaign{..} syntax means that all fields of the 'Campaign' value are in scope (for example 'campaignDeadline' in l. 70).
+        --    See note [RecordWildCards].
+        --
+        -- 2. A 'CampaignAction'. This is the redeemer script. It is provided by the redeeming transaction.
+        --
+        -- 3. A 'CampaignActor'. This is the data script. It is provided by the producing transaction (the contribution)
+        --
+        -- 4. A 'PendingTx' value. It contains information about the current transaction and is provided by the slot leader.
+        --    See note [PendingTx]
+        \Campaign{..} (act :: CampaignAction) (con :: CampaignActor) (p :: PendingTx') ->
+            let
+
+                infixr 3 &&
+                (&&) :: Bool -> Bool -> Bool
+                (&&) = $$(PlutusTx.and)
+
+                PendingTx ps outs _ _ (Height h) _ _ = p
+
+                deadline :: Int
+                deadline = let Height h' = campaignDeadline in h'
+
+                collectionDeadline :: Int
+                collectionDeadline = let Height h' = campaignCollectionDeadline in h'
+
+                target :: Int
+                target = let Value v = campaignTarget in v
+
+                -- | The total value of all contributions
+                totalInputs :: Int
+                totalInputs =
+                    let v (PendingTxIn _ _ (Value vl)) = vl in
+                    $$(P.foldr) (\i total -> total + v i) 0 ps
+
+                isValid = case act of
+                    Refund -> -- the "refund" branch
+                        let
+
+                            contributorTxOut :: PendingTxOut -> Bool
+                            contributorTxOut o = case $$(pubKeyOutput) o of
+                                Nothing -> False
+                                Just pk -> $$(eqPubKey) pk con
+
+                            -- Check that all outputs are paid to the public key
+                            -- of the contributor (this key is provided as the data script `con`)
+                            contributorOnly = $$(P.all) contributorTxOut outs
+
+                            refundable = h > collectionDeadline && contributorOnly && $$(txSignedBy) p con
+
+                        in refundable
+                    Collect -> -- the "successful campaign" branch
+                        let
+                            payToOwner = h > deadline && h <= collectionDeadline && totalInputs >= target && $$(txSignedBy) p campaignOwner
+                        in payToOwner
+            in
+            if isValid then () else $$(P.error) () ||])
 
 -- | The address of a [[Campaign]]
 campaignAddress :: Campaign -> Ledger.Address'
@@ -142,3 +156,22 @@ refundHandler txid cmp = EventHandler (\_ -> do
 
 $(mkFunction 'scheduleCollection)
 $(mkFunction 'contribute)
+
+{- note [RecordWildCards]
+
+We can use the syntax "Campaign{..}" here because the 'RecordWildCards' 
+extension is enabled automatically by the Playground backend.
+
+The extension is documented here:
+* https://downloads.haskell.org/~ghc/7.2.1/docs/html/users_guide/syntax-extns.html
+
+A list of extensions that are enabled by default for the Playground can be found here:
+* https://github.com/input-output-hk/plutus/blob/b0f49a0cc657cd1a4eaa4af72a6d69996b16d07a/plutus-playground/plutus-playground-server/src/Playground/Interpreter.hs#L44
+
+-}
+
+{- note [PendingTx]
+
+This part of the API (the PendingTx argument) is experimental and subject to change.
+
+-}

plutus-playground/plutus-playground-server/usecases/Game.hs

@@ -33,7 +33,7 @@ mkRedeemerScript word =
 
 gameValidator :: ValidatorScript
 gameValidator = ValidatorScript (Ledger.fromCompiledCode $$(PlutusTx.compile [||
-    \(ClearString guess) (HashedString actual) (p :: PendingTx ValidatorHash) ->
+    \(ClearString guess) (HashedString actual) (p :: PendingTx') ->
 
     if $$(P.equalsByteString) actual ($$(P.sha2_256) guess)
     then ()

plutus-playground/plutus-playground-server/usecases/Vesting.hs

@@ -85,7 +85,7 @@ validatorScriptHash =
 validatorScript :: Vesting -> ValidatorScript
 validatorScript v = ValidatorScript val where
     val = Ledger.applyScript inner (Ledger.lifted v)
-    inner = Ledger.fromCompiledCode $$(PlutusTx.compile [|| \Vesting{..} () VestingData{..} (p :: PendingTx ValidatorHash) ->
+    inner = Ledger.fromCompiledCode $$(PlutusTx.compile [|| \Vesting{..} () VestingData{..} (p :: PendingTx') ->
         let
 
             eqPk :: PubKey -> PubKey -> Bool