[plt-scheme] A question about using the ellipsis as a temporary substitute for the program body (among other things).

On Mon, 12 Mar 2007, Lou Oswald Meneses wrote:

> Hi! I am using Dr. Scheme set to Beginning Student and I'm wondering why 
> using the three dots for the purpose I described in the title, as 
> suggested in "How to Design Programs", doesn't work.


Hi Lou,

I think what you mean is that you're seeing the error message:

    ...: name is not defined, not an argument, and not a primitive name in:
        ...

"..." is just a placeholder, so any program that contains it won't execute 
or "Check Syntax" properly until '...' is replaced with whatever it really 
should contain.


What you can do, temporarily, is define '...' to some scratch value at the 
top of your program.  For example:

;;;;;;;;;;;;;;;;;;;;;;;;;
(define ... "fill me in")

;; foo: number -> number
;;
;; Example of writing out a function template:
(define (foo n)
   (cond
     [(zero? n) ...]
     [else ...]))
;;;;;;;;;;;;;;;;;;;;;;;;;

Here, we define "..." to stand for the string value "fill me in".



> I did a quick search at the Help Desk, looked around the preferences, 
> reduced the dots from three all the way to one and even changed the dots 
> to asterisks but, obviously, nothing worked. This seems like a very 
> important feature and I'd be glad to know of any way to use it.

Just to mention: normally, this feature is a good thing, because it'll let 
you catch typos quickly.


Best of wishes!