[Newbies] assorted beginner questions

[Blake]

On Tue, 02 Oct 2007 20:22:01 -0700, Mark Smithfield  
<m_smithfield at yahoo.com> wrote:

> In the floor method from Number,
>
>     truncation _ self truncated.
>
> What does the underscore mean?

:=

In some images it shows up as a left-pointing arrow.

I'm not sure if that's coming back in later iterations or not.

> I want to apply smalltalk to fibonacci numbers. I add
> this method
> to Integer,
>
> fib:
>     (self = 0) ifTrue: (^0)
>     (self = 1) ifTrue: (^1)
>     ^ (self - 1 fib) + (self - 2 fib).
>
> Next, I would like to memoize this method, (because of
> the enormous performance gains).  I do not see how to
> memo-ize things in smalltalk. Can somebody help me see the necessary
> shift in thinking?

I don't see why memoization would be different in Smalltalk. Or why it  
would specifically have to be, rather. You might create a Fibonacci class  
that contained an array or somesuch and cached the numbers that had  
already been called. (Slowly taking up more and more space over time.)