context? error with default function

[Tim Johnson]

I have a context called 'cgi and a default function as in

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(define (cgi:cgi) ;....
  )
Another function in this context executes the following:

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(if (not (context? cgi key))
  (raise (append "key: ['" key "] not previously set")))

Where 'raise is another function in the context.

And I get the following error message

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context expected in function context? : cgi:cgi
Is there a way around this?

thanks

Tim

[rickyboy]

Tim,



I'm not an expert, but when I try to mock up some code for this, I get a different error message, namely:

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ERR: string expected in function context? : key
When I quote key in the context? expression, the error message goes away.

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(if (not (context? cgi "key")) (raise "Bad dog!"))
Hope this helps.  --Rick

[rickyboy]

Oh yes, now I'm getting your error message, Tim.  (I had mocked up the functions incorrectly before.)



The good news is that the solution in my last message (expressing "key" as a string constant) still solves the problem.

[Tim Johnson]

In my code, the symbol 'key has already been coerced to a string.

Thanks

Tim

[Tim Johnson]

You know what? I think there may be a side effect causing this,

and since my wife just informed me that it was my turn to make

dinner, I'm going to abandon this 'til tomorrow. :-)

thanks

and stay tuned

tim

[cormullion]

The manual seems to imply that you have to use a string:

(context? exp str-sym)



[this] syntax checks for the existence of a symbol in a context. The symbol is specified by its name string in str-sym.

Perhaps you can't supply a symbol for evaluation here. Or perhaps you have to coerce it to a string here rather than elsewhere:

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(if (not (context? cgi (string key)))
   ...

[Lutz]

Refer to 'cgi' with 'MAIN:cgi'. The function 'cgi:foo' thinks you are referring to 'cig:cgi', because 'cgi' is define as a local symbol in the context 'cgi'. When you say 'MAIN:cgi' you make clear you mean the context cgi. The local symbol 'sgi' is not a context but a lambda function returning "hello".

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(context 'cgi)

(set 'var 123)

(define (cgi:cgi) "hello")

(define (foo key)
    (if (context? MAIN:cgi key)
(append key " does exist")
        "does not exit"))


(context MAIN)

> (cgi:foo "var")
"var does exist"
> (cgi:foo "bar")
"does not exit"
>


[Tim Johnson]

Thanks Lutz, I'm afraid I wouldn't have thought of that myself.

Can we then say that any context is part of the 'MAIN context?

Tim