calling context functions indirectly

[cormullion]

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

Code Select Expand

(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...?

[rickyboy]

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



--Rick

[cormullion]

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

[Lutz]

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

Code Select Expand

(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

[cormullion]

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...