Thanks for the tip on parameterized constructers; that did help. I think
that I should have been using new rather than boa. I have I changed symtab
and it is uploaded to the website if you want to look at it:
www.rosycrew.org/symtab.factor. I also fixed a bug in optimize that I
discovered.
There is one strange thing that puzzles me. When I use new to create an
object, I get an extra slot in the front. What is that? My tuple looks like
this:
TUPLE: symtab key count left rite ;
When I create one with
symtab new
I get this:
T{ symtab f f f f f }
Notice that there are 5 slots, rather than the 4 that I would have expected.
I have the following code to initialize the tuple:
: <init-symtab> ( key initial-count node -- node )
0 >>left
0 >>rite
swap >>count
swap >>key
;
inline
: init-symtab ( key node -- node )
1 swap <init-symtab> ;
inline
When I create a tuple like this
"simple" symtab new init-symtab
I get this:
T{ symtab f "simple" 1 0 0 }
Notice that my 4 slots are initialized (key="simple", count=1, left=0,
rite=0), but we have a mystery slot in the front that is set to f. This
doesn't prevent the program from running, but it seems to be wasting memory,
and it is confusing me. The boa function did the same thing, but I just
didn't notice it previously. Any idea what that slot might be?
> Message: 7
> Date: Fri, 15 May 2009 14:17:54 +0900
> From: Matthew Willis <[email protected]>
> Subject: Re: [Factor-talk] OOP tutorial
> To: [email protected]
> Message-ID: <[email protected]>
> Content-Type: text/plain; charset=US-ASCII; format=flowed; delsp=yes
>
> Hugh,
>
> I think you should look at "Parameterized constructers" in the help to
> answer your question about arranging parent/child constructors.
>
> About overriding the methods of the parent class: just define a method
> for the child class.
>
> From my experience with OOP in Factor, nearly all code is written as
> "external functions" rather than "member functions". Methods are used
> only in the case that code needs to dispatch based on the type of an
> object. These dispatching words are "low-level" in the sense that
> words that call them don't need to involve dispatching and hence tend
> not to be methods.
>
> The point of Factor OOP (to me) is to allow one to quickly write code
> that does different things for different objects while not forcing one
> to write extra boilerplate for non-dispatching code.
>
> Have fun!
> Matthew Willis
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