IntersectMBO/plutus

Specify the exact meaning of "pure" in the PIR optimizer

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#6,077 opened on May 21, 2024

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Good first issueInternalPlutus IRstatus: triaged

Description

We have that PlutusIR.Purity.isPure and its semantics seems to be underspecified. You can see how it causes confusion here for example.

We need to properly specify the semantics of this function and the entire concept of purity. Ideally, even formalize it. Otherwise we may run into a situation where the PIR optimizer changes the behavior of the program potentially introducing a severe bug into the smart contract.

And do we need the same for UPLC?

Contributor guide

Tech stack
None
Domain
backend
Issue type
research
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
4
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
over 1 week
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
mostly clear
Prerequisites
Understanding of PIR optimizerFamiliarity with Plutus languageKnowledge of purity in programming languages
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
15
Research direction
Examine the function `PlutusIR.Purity.isPure` and its usage in the Plutus codebase. Review the discussion in the linked PR #5093 (https://github.com/input output hk/plutus/pull/5093#discussion r1092117897) to understand the confusion. Specify the semantics of purity for the PIR optimizer, potentially formalizing it, and consider whether the same specification is needed for UPLC.