using (in-readtable) to select a readtable

[Attila Lendvai]

> Problem is that when you issue (in-readtable) form, it can alter
> *readtable-alist*.


it certainly can, but does it? and if it does, then why? let's change
it so that it doesn't alter *readtable-alist*!


> E.g. let's assume that :foo package is assicitated to :foo-readtable.
> Then consider the following call sequence in REPL:
>
> (in-package :foo)
> (in-readtable :bar-readtable)
>
> Then :foo package is associated to bar-readtable.


why? that sounds confusing to me. i see no reason for in-readtable to
touch *readtable-alist*.


> Also, if there are two source files where package is the same while
> readtables are different between the files, readtable associtated to
> package changes implicitly as a side-effect of file compilation or
> loading.


that should not happen, i consider such a behavior a bug.


> E.g. this can occur after we edit either file and then load
> asdf system which contains both files. Then consider we are going to
> SLIME REPL and do (in-package). Then we assume that readtable changed
> implicitly, but it can change to value from either file, in dependence
> of our editing activity.
>
> *lock-readtable-alist* would protect from this situation.


that's unjustified complexity. plus a concurrency lock would not solve
the problem you described above.

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• attila lendvai
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