judgment-form generation failure when variable-not-otherwise-mentioned combines with variable-not-in
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- Dominant language
- Racket
- Stars
- 112
- Forks
- 42
- PR merge metrics
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Description
The call to generate-program here always fails:
#lang racket
(require redex/reduction-semantics)
(define-language L
(x ::= variable-not-otherwise-mentioned (list x)))
(define-judgment-form L
#:mode (J I I O)
[(where x ,(variable-not-in (term (x_a x_b)) 'q))
------------------
(J x_a x_b x)])
(generate-term L #:satisfying (J any_1 any_2 any_3) 4)
The issue seems to be in the ground-or-ok function: https://github.com/racket/redex/blob/745e22c32359a469a2925156b902ba1550e9e378/redex-lib/redex/private/jdg-gen.rkt#L31 which doesn't seem to be treating variable-not-in properly.
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First steps
- Read the whole issue, then the project's contributing guide.
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Research direction
Start by running the supplied Racket example and inspect ground-or-ok in redex-lib/redex/private/jdg-gen.rkt at the linked location. Trace how variable-not-otherwise-mentioned and variable-not-in are handled during judgment-form generation; done means the generate-program call no longer fails for this reproduction.
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
- Clearly specified
- Newbie friendliness
- 45/100