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Add a page comparing Plutus V1, V2 and V3 (#6400)
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‎doc/docusaurus/docs/working-with-scripts/exporting-scripts-datums-redeemers.md‎

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# Exporting scripts, datums and redeemers
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> :pushpin: **NOTE**
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>
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> This guide uses the scripts from the topic [Writing basic validator scripts](writing-basic-validator-scripts.md).
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Since scripts must match their on-chain hashes exactly, it is important that the scripts which an application uses do not accidentally change.
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For example, changing the source code or updating dependencies or tooling may lead to small changes in the script.
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As a result, the hash will change.
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For example, changing the source code or updating dependencies or tooling may lead to small changes in the script.
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As a result, the hash will change.
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In cases where the hashes must match exactly, even changes which do not alter the functionality of the script can be problematic.
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For this reason, once you expect that you will not modify the on-chain part of your application more, it is sensible to *freeze* it by saving the final Plutus Core to a file.
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Additionally, while most Plutus Applications use scripts by directly submitting them as part of transactions from the application itself, it can be useful to be able to export a serialized script.
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Additionally, while most Plutus Applications use scripts by directly submitting them as part of transactions from the application itself, it can be useful to be able to export a serialized script.
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For example, you might want to submit it as part of a manually created transaction with the Cardano node CLI, or send it to another party for them to use.
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Fortunately, it is quite simple to do this.
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Most of the types have typeclass instances for `Serialise` which allows translating directly into CBOR.
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Fortunately, it is quite simple to do this.
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Most of the types have typeclass instances for `Serialise` which allows translating directly into CBOR.
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This applies to `Validator`, `Redeemer`, and `Datum` types.
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If you want to create values that you can pass to the Cardano CLI, you will need to convert them to the appropriate types from `cardano-api` and use `serialiseToTextEnvelope`.
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{-# OPTIONS_GHC -fplugin-opt PlutusTx.Plugin:dump-uplc #-}
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```
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This will dump the output to a temporary file with a name based on the module name.
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The filename will be printed to the console when compiling the source file.
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This will dump the output to a temporary file with a name based on the module name.
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The filename will be printed to the console when compiling the source file.
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You can then move it to a more permanent location.
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It can be read in conveniently with `loadFromFile` as an alternative to `compile`.
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<LiteralInclude file="BasicValidators.hs" language="haskell" title="Block Title" start="-- BLOCK6" end="-- BLOCK7" />
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‎doc/docusaurus/docs/working-with-scripts/ledger-language-version.md‎

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---
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sidebar_position: 1
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---
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# Plutus Ledger Language Version (Plutus V1/V2/V3)
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As explained in [Different Notions of Version](../essential-concepts/versions.md), Plutus V1, V2 and V3 are not distinct programming languages; the primary difference lies in the arguments the script receives from the ledger, and the value it returns.
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Therefore, Plutus V1, V2 and V3 can be understood as type signatures, in the sense that they each represent a subset of Untyped Plutus Core (UPLC) programs with specific types.
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Any UPLC program that matches the expected argument and return types can be considered and used as a Plutus V1, V2 or V3 script.
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Next we'll start with a brief overview of the script context, followed by an in-depth explanation of these type signatures.
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## ScriptContext
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Every Plutus script receives an argument called script context.
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It contains information about the transaction the script is validating, such as inputs, outputs, transaction fee, signatures and so on.
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Additionally, since a transaction may have multiple things to validate (e.g., it may be spending multiple script UTXOs, or performing both spending and minting), each of which is validated by a separate script, the script context also has a script purpose field, telling the script what exactly it is supposed to validate.
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Plutus V1, V2 and V3 scripts receive different script contexts even when all else is equal.
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This is because different ledger language versions are introduced in different ledger eras; transactions in different ledger eras have different fields - a new era usually adds new fields and may also change existing fields.
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As a result, The script contexts for Plutus V1, V2 and V3 also have different fields, leading to different Haskell types ([V1](https://plutus.cardano.intersectmbo.org/haddock/master/plutus-ledger-api/PlutusLedgerApi-V1-Contexts.html#t:ScriptContext), [V2](https://plutus.cardano.intersectmbo.org/haddock/master/plutus-ledger-api/PlutusLedgerApi-V2-Contexts.html#t:ScriptContext), [V3](https://plutus.cardano.intersectmbo.org/haddock/master/plutus-ledger-api/PlutusLedgerApi-V3-Contexts.html#t:ScriptContext)).
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We cannot modify the script context fields of an existing ledger language version once it is published, since it would break existing scripts.
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In general, a ledger language version cannot be used in a transaction, if the ledger language version was introduced in ledger era A, the transaction uses features in ledger era B, and A is earlier than B.
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For instance, Plutus V1 (introduced in the Alonzo era) scripts cannot be used in a transaction which utilizes inline datum (a Babbage era feature); Plutus V2 (introduced in the Babbage era) scripts cannot be used in a transaction that registers a DRep (introduced in the Conway era)[^1].
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## Plutus V1 and Plutus V2
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Plutus V1 and Plutus V2 scripts have four [script purposes](https://plutus.cardano.intersectmbo.org/haddock/master/plutus-ledger-api/PlutusLedgerApi-V1-Contexts.html#t:ScriptPurpose): spending, minting, certifying, and rewarding[^2].
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The arguments a Plutus V1 or V2 script receives depend on the script purpose.
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There is no requirement on the return value of a Plutus V1 and V2 script: script evaluation succeeds as long as the evaluation terminates without error, and the execution budget is not exceeded.
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### Spending Scripts
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A Plutus V1/V2 spending script receives three arguments corresponding to datum, redeemer and script context.
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All arguments are encoded as `BuiltinData`.
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Thus in Plutus Tx, a spending script has the following type:
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```haskell
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BuiltinData -> BuiltinData -> BuiltinData -> any
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```
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To create a Plutus script using Plutus Tx, it is common to first write a function that takes the corresonding Haskell domain types and returns `Bool`.
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For example, the following function can be used to implement the main business logic of a Plutus V1 spending script:
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```haskell
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myV1SpendingScriptTyped :: MyDatum -> MyRedeemer -> PlutusLedgerApi.V1.ScriptContext -> Bool
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```
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where `MyDatum` and `MyRedeemer` are your user-defined Haskell types specific to your contract.
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If you are writing a Plutus V2 script, use `PlutusLedgerApi.V2.ScriptContext`.
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From `myV1SpendingScriptTyped`, you can obtain `BuiltinData -> BuiltinData -> BuiltinData -> any`, and subsequently compile it to UPLC, via
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```haskell
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myV1SpendingScriptUntyped :: BuiltinData -> BuiltinData -> BuiltinData -> BuiltinUnit
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myV1SpendingScriptUntyped myDatum myRedeemer scriptContext =
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PlutusTx.Prelude.check
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( myV1SpendingScriptTyped
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(PlutusTx.unsafeFromBuiltinData myDatum)
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(PlutusTx.unsafeFromBuiltinData myRedeemer)
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(PlutusTx.unsafeFromBuiltinData scriptContext)
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)
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myV1SpendingScriptCompiled :: CompiledCode (BuiltinData -> BuiltinData -> BuiltinData -> BuiltinUnit)
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myV1SpendingScriptCompiled = $$(PlutusTx.compile [||myV1SpendingScriptUntyped||])
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```
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`unsafeFromBuiltinData` is a method from the [`UnsafeFromData`](http://localhost:3000/docs/working-with-scripts/ledger-language-version) class.
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Each call to `unsafeFromBuiltinData` decodes a `BuiltinData` into a value of a Haskell domain type, failing if the conversion fails.
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The `check` function takes a `Bool` and returns a `BuiltinUnit`, throwing an error if the input is `False`.
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It is needed because returning `False` does not cause the validation to fail; to fail the validation, an error needs to be thrown.
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In this example the script happens to return `BuiltinUnit`, but this is not a requirement for Plutus V1 or V2.
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### Minting, Certifying and Rewarding Scripts
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Unlike spending scripts, Plutus V1 and V2 scripts for minting, certifying and rewarding purposes take one fewer argument: there is no datum argument.
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Thus in Plutus Tx, a minting, certifying or rewarding script should have the following type:
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```haskell
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BuiltinData -> BuiltinData -> any
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```
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Since this type signature is shared by minting, certifying and rewarding scripts, the same script can be used for multiple of these three purposes, for example
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```haskell
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myV1MintingAndRewardingScriptTyped :: MyRedeemer -> PlutusLedgerApi.V1.ScriptContext -> Bool
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myV1MintingAndRewardingScriptTyped myRedeemer scriptContext =
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case scriptContextPurpose scriptContext of
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Minting cs -> -- Perform minting validation
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Rewarding cred -> -- Perform rewarding validation
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```
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Because spending scripts take one more argument, the same script cannot be used both for spending validation and for a different purpose (minting, certifying or rewarding).
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### Script Evaluation and Unsaturated Scripts
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As said before, evaluating a Plutus V1 and V2 script succeeds as long as the evaluation terminates without error, and the budget is not exceeded.
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This means, crucially, that an unsaturated script (a script expecting more arguments than it receives) succeeds trivially, since the evaluation terminates almost immediately and returns a lambda.
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Thus be careful: if, for example, you accidentally use a spending script (which expects three arguments) as a minting script (which will receive two arguments), it will always succeed, which is obviously not what you want.
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## Plutus V3
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Plutus V3 has two additional [script purposes](https://plutus.cardano.intersectmbo.org/haddock/master/plutus-ledger-api/PlutusLedgerApi-V3-Contexts.html#t:ScriptPurpose) for validating governance actions: voting and proposing.
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Besides the usual differences between different Plutus ledger language versions, there are three additional key differences between Plutus V3 and V1/V2:
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1. All Plutus V3 scripts, regardless of script purpose, take a single argument: the script context.
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The datum (for spending scripts) and the redeemer are part of the Plutus V3 script context.
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This means the same script can be used for spending validation and for different purposes.
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2. The datum is now optional for spending scripts.
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The script context may or may not contain a datum, depending on whether the UTXO being spent has a datum associated with it.
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3. There is an additional condition for the evaluation of a Plutus V3 script to be considered successful: the return value must be a `BuiltinUnit`.
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The first two points are attributed to [CIP-69](https://developers.cardano.org/docs/governance/cardano-improvement-proposals/cip-0069/), whereas the third point is attributed to [CIP-117](https://developers.cardano.org/docs/governance/cardano-improvement-proposals/cip-0117/).
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In other words, all Plutus V3 scripts should have the following type in Plutus Tx:
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```haskell
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BuiltinData -> BuiltinUnit
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```
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Updating a Plutus V1/V2 script to turn it into a Plutus V3 script mostly involves straightforward refactoring, except that for a spending script, the case where the datum is absent will need to be handled.
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---
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[^1]: There is one exception to this: Plutus V1 can be used in transactions with reference inputs, even though reference inputs were introduced in the Babbage era.
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[^2]: For more information on script purposes, refer to [Script Purposes](script-purposes.md).

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