Why does the starting namespace for ⍵⍵ change based on ⍺⍺?

General APL language issues

Re: Why does the starting namespace for ⍵⍵ change based on ⍺

Postby Vince|Dyalog on Tue Oct 13, 2020 3:55 pm

Hi Phil,

Bug 17 is fixed in 18.0.

There are issues with the fix and calling dfns from within dfns with ⍎ or via trad ops.

You can find more details about it here:

"Issues with mixed Lexical and Dynamic Scope" https://www.dyalog.com/news/141/420/Introducing-Dyalog-Version-18-0-Issue-2.htm

Regards,

Vince
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Re: Why does the starting namespace for ⍵⍵ change based on ⍺

Postby petermsiegel on Tue Oct 13, 2020 4:12 pm

Thanks so much, all, for investigating.

The interesting thing about this bug is it's so easy to write concise, reasonable code that surprises you (or worse, works incorrectly without giving notice). Even if you don't change classes of operands willy-nilly, you'd expect to be able to reason about what the starting namespace is for each operand and for the operator itself. OTOH, there is an easy workaround, when you are aware of the problem.
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