newlispfanclub.alh.net

Posted: **Thu May 24, 2007 8:20 pm**

When applying a function defined in a context to a table defined outside of that context, how can you do assoc lookups? For example:

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(context 'foo)
(define (some-fn table)
  (lookup 'key-a table))

(context 'bar)
(some-fn '((key-a "value-a") (key-b "value-b")))

some-fn may be used from various contexts. In order to lookup key-a, it must know which context we are coming from. I can do a (name table true), but then to get the correct symbol to look up, I'm forced to do something like:

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(eval-string (format "%s:key-a" (string (name table true)))

...which is incredibly verbose syntax just for a table lookup. Anyone have a solution?

Posted: **Fri May 25, 2007 1:12 pm**

Never mind. I've figured it out.

If I create the list in question inside of a context, and then I can pass the context to the function in another context. With the example above:

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(context 'foo)
(define (some-fn ctx)
  (lookup 'ctx:key-a ctx:table))

(context 'bar)
(set 'table ((key-a "value-a") (key-b "value-b")))

(context 'whatever)
(foo:some-fn bar)

Now, foo is reading the context of the input, and can lookup based on the context's symbols in the context's lists.

Posted: **Fri May 25, 2007 3:11 pm**

... and as an added benefit you have passed your bar:table by reference, which is nice if your are dealing with a lot of data.

Lutz

Posted: **Fri May 25, 2007 4:00 pm**

I always prefer to do lots of work at the bar:table. Preferably with a glass:full ;)

Posted: **Sat May 26, 2007 5:09 pm**

Jeff wrote:I always prefer to do lots of work at the bar:table. Preferably with a glass:full ;)

[Click here for audio response.] :-)

newlispfanclub.alh.net

Contexts question

Contexts question