On Tuesday 29 July 2008 14:44:00 Joe Groff wrote:
> And is there any way to distinguish defining a new word in the current
> vocab from adding a method to a generic in an imported method?
The method syntax works on words in the "current" vocabulary. So if you want
to extend a generic from another vocabulary, you put an explicit 'IN:' there.
For example, if I want to extend the sequences 'nth' from one of my own
vocabularies, I'd do:
IN: my-vocab
...
...
! Extend 'nth' from 'sequences':
IN: sequences
: nth ... ;
! Switch back to my-vocab:
IN: my-vocab
...
That's doing things in a very manual way however. It would be nice to declare
at the top of the vocabulary:
EXTEND: nth sequences
So you're saying "extend 'nth' from the 'sequences' vocabulary". How would
this be implemented? Look at how word names are resolved in
the 'method-syntax' implementation:
: name>word ( name -- word )
dup in get lookup dup
[ nip ]
[ drop in get create ]
if ;
Nice and simple; we only pick words from the 'in' vocabulary. What
the 'EXTEND:' word would do is add that generic word to a list.
Then 'name>word' would check that list as well as the 'in' vocabulary.
Now the above example looks like:
IN: my-vocab
EXTEND: nth sequences
...
This is even *better* than the current state of affairs. Right now, when
you're reading code, you'll see folks adding methods but it's not clear what
vocabulary the generic is from unless you look it up manually. This way, it's
clear from the declaration which generics are being extended. This also
clears up possible problems that can result from the order of items in
the 'USING:' form.
If you are extending a ton of generics from a particular vocabulary, it's
probably better to fall back to using 'IN:':
IN: my-vocab
...
IN: sequences
... define lots of methods
IN: my-vocab
Which might look better than:
IN: my-vocab
EXTEND: abc sequences
EXTEND: def sequences
EXTEND: ghi sequences
...
I.e. you'd need an 'EXTEND:' for every generic you're extending. Thus
the 'IN:' is a cleaner route.
If you don't explicitly use 'IN:' or 'EXTEND:', then a new generic will be
created in the current vocabulary.
Ed
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