Scalus Integration

Scalus compiles a subset of Scala to Plutus Core, the language of Cardano smart contracts. Its Cardano Client Lib integration also works from plain Java, where you can use it to evaluate script costs locally and to apply parameters to compiled scripts.

Scalus runs on the JVM and bundles native libraries for macOS, Windows and Linux, including ARM64 Linux, which Aiken Java Binding doesn’t support.

Dependencies

Maven (pom.xml)

<dependency>
    <groupId>org.scalus</groupId>
    <artifactId>scalus-bloxbean-cardano-client-lib_3</artifactId>
    <version>1.4.1</version>
</dependency>

Gradle (build.gradle)

implementation 'org.scalus:scalus-bloxbean-cardano-client-lib_3:1.4.1'

This Scalus release declares a dependency on Cardano Client Lib 0.7.3. We tested it with the latest preview on a local devnet and on Preview. Gradle picks the higher version by itself. With Maven, declare cardano-client-lib directly in your pom.xml so that your version wins.

Script Cost Evaluation

ScalusTransactionEvaluator implements the library’s TransactionEvaluator interface, so you can pass it directly to the QuickTx builder.

ProtocolParams params = backendService.getEpochService().getProtocolParameters().getValue();
UtxoSupplier utxoSupplier = new DefaultUtxoSupplier(backendService.getUtxoService());

TxResult result = quickTxBuilder.compose(tx)
        .feePayer(address)
        .withSigner(SignerProviders.signerFrom(account))
        .withTxEvaluator(new ScalusTransactionEvaluator(SlotConfig.preview(), params, utxoSupplier))
        .completeAndWait();

SlotConfig is scalus.cardano.ledger.SlotConfig, and it also has mainnet() and preprod(). A script needs the right one to read a transaction’s validity range correctly.

If the transaction uses reference scripts, add a script supplier so that the evaluator can read them:

new ScalusTransactionEvaluator(SlotConfig.preview(), params, utxoSupplier,
        new ScriptServiceSupplier(backendService.getScriptService()))

See Calling a Plutus script for a complete example.

Apply Script Parameters

ScalusScriptUtils.applyParamsToScript applies parameters to a script. It takes and returns double-encoded CBOR hex, which is what PlutusScript.getCborHex() holds. A blueprint’s compiledCode is single-encoded, so load it as a script first:

PlutusScript unapplied = PlutusBlueprintUtil.getPlutusScriptFromCompiledCode(compiledCode, PlutusVersion.v3);

String applied = ScalusScriptUtils.applyParamsToScript(unapplied.getCborHex(), BytesPlutusData.of(issuerKeyHash));

PlutusV3Script script = PlutusV3Script.builder()
        .type("PlutusScriptV3")
        .cborHex(applied)
        .build();

The method also accepts a ListPlutusData. For the same inputs, we confirmed that the result matches AikenScriptUtil.applyParamToScript.