🚀 go-pugleaf

Stephen P Spackman:
   ... you have just substituted the words "programme text" and
   "routine" for "scope".  What do these things look like? What is the
   actual domain of the definition?

I'm not sure I understand the questions.  J hasn't been around long
enough for there to be a particular definition style.  For example, a
style which uses a separate file for each function definition would
look quite different than a style which uses scripts, with literal
text quoted in-line.  The first would look somewhat like a c program
with various modules and a makefile, the second would look somewhat
like a shar archive (or, perhaps, a bit cleaner).  And if the user is
driving the definition process from emacs, they'll just look like
text.  And, there are other definition styles.

If by "domain of the definition" you mean the domain of the thing
which is defined, well, that depends on the definition.  Domain, in
this sense, is more or less independent of the mechanisms used for
definition. 

   Oh, I realise there's still a missing piece of info: if you use =:
   in a scope that has introduced a new name textually identical to
   that on the left of the assignment, what gets updated? The local,
   the global, or both? If you are really LEXICALLY scoped, it ought
   to be the local, but what if that defining scope has already
   exited? Is that handled correctly?

Well, the global definition is updated.  If you want the local
definition to be updated you can use '=.'  If there is some local
definition shadowing the global definition, you can always create a
new context where the local definition does not exist.

I might define an example of this as follows:

example =. (here_is '.') : ''
.  test=. 3
.  test=: 4
. 'local  ' label test
. 'global ' label 'test':'' 0
.                               NB. return an empty result

Then, if I used
   example 0
The routine would display:
local  3
global 4

And, on exit, 'test' would have the value 4

By the way, I'm presuming that the definitions of 'here_is' and
'label' are not pertinent to this discussion.  Also, 'NB.' introduces
a comment.


-- 
Raul Deluth Miller-Rockwell                   <rockwell@socrates.umd.edu>