Redex v6.4 "broke" LambdaJS

[natash...@brown.edu]

(For some reason the mail I sent to users<at>racket-lang.org last week never made it to the Google Group, so I'm posting directly...)

Hello,

I'm a 2nd year PhD student working with Shriram Krishnamurthi on improving Redex's testing/checking performance and capabilities.

I was looking to use LambdaJS (http://cs.brown.edu/research/plt/dl/jssem/v1/) as a case study, but unfortunately jscore.ss does not compile under the latest version of Redex.

The shortcut used in the eval reduction relation
...
with
[(--> (σ (in-hole E e_1)) (σ (in-hole E e_2)))
(==> e_1 e_2)]))
now throws an error "reduction-relation: shortcut name may not be a non-terminal in: e_1."

I believe this was caused by the following change (https://github.com/racket/redex/blob/master/redex-lib/redex/HISTORY.txt) in Redex v6.4:

changed shortcuts in --> so that non-terminals are no
longer allowed for the names in the shortcut "parameters"
These shortcut names were never constrained to actually be
non-terminals, so this change is intended entirely to be
able to give a helpful error message in an attempt to avoid
confusion

As a Redex novice, I'm failing to avoid confusion in this case. Any advice on a simple way to change the shortcut / reduction relation to respect this change in Redex is greatly appreciated.

Thanks for the help!

[Ben Greenman]

I think it'll work if you delete the underscores, e.g. change "e_1" to "e1".

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[Sam Caldwell]

History behind this change: https://groups.google.com/d/msg/racket-users/1SVVqsg4ARQ/vVxKiAvaAQAJ
Relevant commit: https://github.com/racket/redex/commit/cbb2d88b98fb814325f0d4ee468e1abaf4f6c3a7

So changing e_1 and e_2 to be anything that is *not* a non-terminal in your model should do the trick.

-Sam Caldwell

[natash...@brown.edu]

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Thank you for the relevant group posting... I see, it's an identifier because it is in the context of a shortcut. I was mistaking the type of e_1 to be a pattern in the context of inner in-hole. Unfortunately, I did not parse 'shortcut name' in the error message to mean 'shortcut name for an expected identifier.' Thanks for the clarification!