racket / racket/redex

`cross` plus small grammar causes infinite loop in term generation

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Dominant language
Racket
Stars
112
Forks
42
PR merge metrics
No merged PRs in 30d

Description

The program:

#lang racket
(require redex/reduction-semantics)

(define-language esterel-check
  (p ::= nothing (ρ θ p))
  (θ ::= · (S θ)))

(redex-check
 esterel-check
 (cross p)
 (displayln "running")
 #:attempts 100)

Never prints running and eventually consumes all my memory.

This seems to be new behavior since 4bb07c7baa2cb33. I am current on git HEAD.

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Research direction

Start by running the supplied #lang racket reproduction and inspect redex-check term generation for (cross p) with the esterel-check grammar. Compare behavior with commit 4bb07c7baa2cb33; done means the 100 attempts complete without unbounded memory use and the program reaches the displayln call.

Written by the indexing model from the issue text.

Assessment

Domain
compilers
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
30/100

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