Hi Hugh,
That's not a slot, its just part of the syntax. There are two forms of
tuple literal:
TUPLE: point x y ;
T{ point { x 1 } { y 2 } }
T{ point f 1 2 }
Both are equivalent. With the former you name slots with the latter
you write 'f' followed by slot values in order.
Slava
On Mon, May 18, 2009 at 7:42 PM, Hugh Aguilar <[email protected]> wrote:
> 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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