[Newbies] Undeclared variable issue

Roel Wuyts Roel.Wuyts at ulb.ac.be
Wed Sep 6 08:38:20 UTC 2006


| n |
n := 5 factorial.
n printString

Some more explanation: -> is a binary message sent to a receiver  
object to create an association (an instance of class Association  
that is basically a key/value pair). For example, inspect the result  
of the following expression in a workspace:

3 -> 4

In your original piece of code, when you do n -> 5, variable n is  
indeed undefined, and if you proceed it will create an association  
between the 'nil' object (yes, it is a real object as well) and 5.

If you want, you can look up the implementation of the selector ->,  
for example by using the Selector Browser in your tools flab (the one  
at the right), and you will then find that there is a method -> on  
class Object with the following implementation:

-> anObject
	"Answer an Association between self and anObject"

	^Association basicNew key: self value: anObject

On 05 Sep 2006, at 20:17, Edward A. Waugh wrote:

> The following code doesn't execute in my Squeak workspace
> | n |
> n <- 5 factorial.
> n printString
> because it insists that n is undeclared despite that I have declare  
> the it in the first line of the 3 line code fragment.  (I highlight  
> all 3 lines and use the "do it" to execute it.)
> What is going here - this is valid Smalltalk syntax?
> Thanks,
> Edward
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