Example:
I have written my own cgi context. It has a number of control
variables (think symbols)
I want to - if necessary customize those symbols on startup.
I have a context method call 'on.
;; Intialize the CGI object
(cgi:on 'cs nil 'placeholder true) ;; assumes that 'cs and 'placholder
;; are already defined
Inside of the 'on method, a helper function called 'parse-args
intercepts args and processes them two at a time as follows:
(define (parse-args)
(let((key)(val))
(dolist (item (explode (args)))
(set 'key (last(parse(string(first(first item)))":")))
(set 'val(second(first item)))
(set (sym key) val))) ;; reset the symbol
)
As written, I may mistakenly submit a symbol that is not predefined
in the context. I would like to be able to test whether that symbol
is already defined and throw an error if not. I like error messages!
I'd welcome some suggestions on how to proceed.
Thanks
Tim
> (context 'cgi 'xxx 33)
33
> xxx
nil
> cgi:xxx
33
(cgi:xxx)
>
Is
(symbol? exp)
Evaluates the exp expression and returns true if the value is a symbol; otherwise, it returns nil.
(context? ctx "symbol")
Quote from: "Jeff"
Hello Jeff:
A quick test suggests that this is what I'm after.
Thanks
Tim