I noticed this last week when I upgraded Redex for other reasons. It broke one of my models, and I was momentarily confused. In fact, I took the error message to mean I had somehow introduced an error and spent some time staring at my tests to see if I had introduced a syntax error. I only fixed the issue after investigating the git commits to Redex.
It is a little confusing that, in this one place (AFAIK), I have to arbitrary names rather than non-terminal names. It is also strange that my context non-terminal do not trigger this error. That is, with non-terminals E and e defined, [(--> (in-hole E e_0) (in-hole E e_1)) ...] triggers an error while [(--> (in-hole E e0) (in-hole E e1))] does not; perhaps this is just my misunderstanding of how reduction-relation works. -- William J. Bowman On Sat, Dec 19, 2015 at 09:12:53AM -0600, Robby Findler wrote: > I've recently pushed a change to Redex > (https://github.com/racket/redex/commit/cbb2d88b) that disallows the > names of non-terminals in shortcuts in reduction relations. I did this > after seeing someone (quite reasonably!) assume that using a > non-terminal there meant the shortcut would work only for terms > matching those non-terminals, which is not how things actually work. > > The upside of making this an error is that, instead of having to study > the minutiae of the reduction-relation-relation construct in the docs, > Redex users are told when they think redex is fancier than it is in > this respect. > > The downside is that this broke a bunch of old models I had lying > around. I've fixed them (it's easy to do), but I worry that someone > who gets out an old model to show it to someone will be greeted with > this unexpected error message. > > Any opinions on whether or not I should revert this commit? > > Robby > > -- > You received this message because you are subscribed to the Google Groups > "Racket Users" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > For more options, visit https://groups.google.com/d/optout. -- You received this message because you are subscribed to the Google Groups "Racket Users" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout.
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