SWOOP and Context

I finally started looking at SWOOP. I'm confused over context
switching of the search order. From the user manual, I started
off with a simple class definition:

    class mypt
        variable x
        variable y
        : show ( -- ) x @ . y @ . ;
        : dot ( -- ) ." Point at " show ;
    end-class

Next, I defined a static instance:

    mypt builds bar
    5 bar x !
    8 bar y !

I noticed that in storing the variables above, 'bar' adds the
class wordlist and, say, 'x' removes it. Likewise, a colon
member also removes the class wordlist. That makes sense.

I also experimented with the dynamic manipulation words 'using'
and '->' applied to a static instance.

'bar using mypt dot' or '3 bar using mypt x !' work fine.

However, 'bar -> dot' and '3 bar -> x !' worked but changed the
context. '->' and 'calling' fail to restore the context. One
needs to write, for example, 'bar -> dot previous'. Apparently,
since 'calling' or '->' are usually used stored addresses that
haven't changed the context in the first place, it was felt there
was no need to restore the context. Is that right?

Next, I tried out a dynamic instance:

    mypt new value foo
     8 foo using mypt x !
    99 foo calling y !

I noticed that 'using mypt' changed context but 'x' restored it.
Also, 'calling' or '->' had no effect on context. So no
surprises.

One last example for this post. The examples from the manual for
using [objects ... objects].

    : try ( addr -- )
        [objects mypt names sam objects]
        sam dot ;

    : test ( -- )
        [objects mypt makes joe objects]
        12 joe using mypt x !
        15 joe using mypt y !
        joe try ;

Although defining 'try' was uneventful, defining 'test' changed
the context. Is this a bug? Generally, when context is changed
during a definition, it's restored at the end (such as with CODE
name ... end-code).

Executing either of these two words appears to neither change nor
restore context.

'foo try' has no context effect and although 'bar try' does, it's
from 'bar' changing context. Until I get this down, I'll be
using OFAD often ( : OFAD only forth also definitions ) :-)

Bill
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Received on Sun Feb 16 2003 - 06:51:11 PST