Plutus.V2.Ledger.EvaluationContext

• Plutus V2 EvaluationContext Tutorial

  Table of Contents

  1. 📖 Introduction

  2. 🔙 Module Re-exports 2.1 🔄 Re-exporting V1.EvaluationContext

  3. ⚙️ Cost Model Parameter Names 3.1 ⚙️ costModelParamNames

  4. 📝 Code Walkthrough

  5. 📖 Glossary of Terms

  1. 📖 Introduction

  This tutorial covers the Plutus.V2.Ledger.EvaluationContext module, which builds upon the V1 evaluation context and exposes the set of valid cost model parameter names for Plutus V2.

  2. 🔙 Module Re-exports

  2.1 🔄 Re-exporting V1.EvaluationContext

  module Plutus.V2.Ledger.EvaluationContext
      ( module V1.EvaluationContext
      , costModelParamNames
      ) where
  
  import Plutus.V1.Ledger.EvaluationContext as V1.EvaluationContext hiding (costModelParamNames)

  • What happens here: The entire V1 evaluation context API is made available under V2, except the old costModelParamNames, so you can reuse all existing context-building functions.

  3. ⚙️ Cost Model Parameter Names

  The key addition in this module is the costModelParamNames set, defining which cost model parameters are valid under Plutus V2.

  3.1 ⚙️ costModelParamNames

  costModelParamNames :: Set.Set Text.Text
  costModelParamNames = Map.keysSet $ fromJust Plutus.defaultCostModelParams

  • Type: Set.Set Text.Text — a set of textual parameter names.

  • Implementation:

    1. Plutus.defaultCostModelParams provides a Maybe (Map Text Text Integer) of default parameters.

    2. fromJust extracts the map (unsafe if defaults missing).

    3. Map.keysSet yields the set of keys (parameter names).

  4. 📝 Code Walkthrough

  1. Imports:

     • Plutus.V1.Ledger.EvaluationContext is brought in as V1.EvaluationContext.

     • PlutusCore.defaultCostModelParams gives the V2 defaults.

     • Standard Haskell libraries for Map, Maybe, Set, and Text.

  2. Re-exporting: All V1 context functions (e.g., mkEvaluationContext, CostModelApplyError) are available without change.

  3. Parameter Names: Use this set to validate incoming cost model parameters when syncing on-chain cost settings.

  5. 📖 Glossary of Terms

  Term	Definition
  V1.EvaluationContext	The original Plutus V1 evaluation context API.
  defaultCostModelParams	Built-in default cost-model parameters from Plutus Core.
  Set.Set Text.Text	A collection of unique Text values.
  Map.keysSet	Extracts the set of keys from a Map.
  fromJust	Unsafe extractor from Maybe, crashes on Nothing.