Documentation

Errors that can be thrown when evaluating a Plutus script.

An opaque type that contains all the static parameters that the evaluator needs to evaluate a script. This is so that they can be computed once and cached, rather than being recomputed on every evaluation.

Different protocol versions may require different bundles of machine parameters, which allows us for example to tweak the shape of the costing function of a builtin, so that the builtin costs less. Currently this means that we have to create multiple DefaultMachineParameters per language version, which we put into a cache (represented by an association list) in order to avoid costly recomputation of machine parameters.

In order to get the appropriate DefaultMachineParameters at validation time we look it up in the cache using a semantics variant as a key. We compute the semantics variant from the protocol version using the stored function. Note that the semantics variant depends on the language version too, but the latter is known statically (because each language version has its own evaluation context), hence there's no reason to require it to be provided at runtime.

To say it differently, there's a matrix of semantics variants indexed by (LL, PV) pairs and we cache its particular row corresponding to the statically given LL in an EvaluationContext.

The reason why we associate a DefaultMachineParameters with a semantics variant rather than a protocol version are

1. generally there are far more protocol versions than semantics variants supported by a specific language version, so we save on pointless duplication of bundles of machine parameters
2. builtins don't know anything about protocol versions, only semantics variants. It is therefore more semantically precise to associate bundles of machine parameters with semantics variants than with protocol versions

The type of the executed script's accumulated log output: a list of Text.

It will be an empty list if the VerboseMode is set to Quiet.

A simple toggle indicating whether or not we should accumulate logs during script execution.

Evaluates a script, with a cost model and a budget that restricts how many resources it can use according to the cost model. Also returns the budget that was actually used.

Can be used to calculate budgets for scripts, but even in this case you must give a limit to guard against scripts that run for a long time or loop.

Note: Parameterized over the LedgerPlutusVersion since 1. The builtins allowed (during decoding) differ, and 2. The Plutus language versions allowed differ.

Evaluates a script, returning the minimum budget that the script would need to evaluate successfully. This will take as long as the script takes, if you need to limit the execution time of the script also, you can use evaluateScriptRestricting, which also returns the used budget.

Note: Parameterized over the ledger-plutus-version since the builtins allowed (during decoding) differs.

Evaluate a fully-applied term using the CEK machine. Useful for mimicking the behaviour of the on-chain evaluator.

Create an EvaluationContext given all builtin semantics variants supported by the provided language version.

The input is a Map of Texts to cost integer values (aka CostModelParams, CostModel) See Note [Inlining meanings of builtins].

IMPORTANT: the toSemVar argument computes the semantics variant for each MajorProtocolVersion and it must only return semantics variants from the semVars list, as well as cover ANY MajorProtocolVersion, including those that do not exist yet (i.e. toSemVar must never fail).

IMPORTANT: The evaluation context of every Plutus version must be recreated upon a protocol update with the updated cost model parameters.

Shared helper for the evaluation functions: evaluateScriptCounting and evaluateScriptRestricting,

Given a ScriptForEvaluation:

1) applies the term to a list of Data arguments (e.g. Datum, Redeemer, ScriptContext) 2) checks that the applied-term is well-scoped 3) returns the applied-term