newlispfanclub.alh.net

Posted: **Wed Nov 08, 2006 5:38 pm**

What I'm trying to do here is pass functions and contexts around, but I can't get the functions to execute.

(context 'TEST0)
  (define (TEST0:foo)  
    (println "hi there from TEST0:foo"))
  (define (TEST0:bar)  
    (println "hi there from TEST0:bar"))

(context 'TEST1)
  (define (TEST1:foo)  
    (println "hi there from TEST1:foo"))
  (define (TEST1:bar)  
    (println "hi there from TEST1:bar"))

(context 'TEST2)
  (define (TEST2:foo)  
    (println "hi there from TEST2:foo"))
  (define (TEST2:bar)  
    (println "hi there from TEST2:bar"))
  
(context MAIN)
  (set 'contexts '(TEST0 TEST1 TEST2))
  (set 'functions '({foo} {bar}))
  (dolist (c contexts)
    (map (fn (f) (eval (sym f c))) functions)             ; <- doesn't do what I thought it might :-)
    )

The required output is for all available contexts to run their functions when called upon to do so. eval should be able to execute the function...?

Posted: **Wed Nov 08, 2006 6:09 pm**

Aren't you missing an extra pair of parentheses, i.e. around the eval call?

--Rick

Posted: **Wed Nov 08, 2006 6:54 pm**

rickyboy wrote:Aren't you missing an extra pair of parentheses, i.e. around the eval call?

--Rick

yes, I am! Thanks for spotting that - it wouldn't have looked right to me so i would never have tried it!

cheers

Posted: **Wed Nov 08, 2006 7:50 pm**

Rick's recommendation is correct, but there is an (perhaps easier to understand?) alternative using 'apply':

Code: Select all

(context MAIN)
  (set 'contexts '(TEST0 TEST1 TEST2))
  (set 'functions '({foo} {bar}))
  (dolist (c contexts)
    (map (fn (f) (apply (sym f c))) functions)   
    )

The effect is the same. Rick's extra parenthesis puts the lambda expression contained in the symbol (sym f c) and extracted by 'eval' into an applicative contextus. 'apply' does the same.

Lutz

Posted: **Wed Nov 08, 2006 10:00 pm**

Thanks. "applicative contextus", eh? My Latin is not as fluent as my newlisp these days...

It's been an educational week, what with all that integer business as well...

newlispfanclub.alh.net

calling context functions indirectly

calling context functions indirectly