macros / code construction

[Mario.Wolczko@Eng.Sun.COM (Mario Wolczko)]

Date: Thu, 31 Aug 1995 00:03:54 +0200
From: rainer@physik3.gwdg.de (Rainer Blome)
To: self-interest@self.sunlabs.com
Subject: macros / code construction


yes, i know, macros as in the lisp family are a very unstructured way of
doing things.  i don't actually care for macros, any way to make convenient
the use of useful but awkward idioms would do.

i have heard about beta's facilities in that direction but have only just
printed the tutorial out, so i can't comment on that.  (as always: no
library -> no book on beta :-( )  i like the common lisp/loops method
combination stuff, so i guess i'll like beta, too. 

there are more things that i miss in self:  local methods and evaluation of
literals in the dynamic context (dynamic?  lexical?  what does lexical mean
anyway, when we don't have source-code anymore?).


imagine doing assignment another way.  assignment is a hack (from the
functional point of view).  it manipulates its context.  one should make
that explicit by revealing the reflection involved in assignment.  first
get an object that represents the place (the slot).  that is the reflective
part.  then send it a normal message with the new value as an argument:

(reflect: self slot: "x") store: 1

(buggy, but you know what i mean.  how the slot implements the `store:'
method?  don't you ask! ;-)

of course, this is to be put as a method in the `assignment slot'.  now
this `slot:' (meta-) message will always eval to the same object (the `x'
slot), so it should not be computed every time the assignment method is
called.

note that the method now _explicitly_ `knows' the slot it refers to, as
opposed to knowing that implicitly by reflecting on its (the method's) own
slot name.  randy and dave mentioned a very similar way to implement
assignment in their ecoop95 paper.

to make this scheme feasible, two things are missing (that means, i
can't see them, *I* might be missing them, not self, tell me if i do.):

    a way to do computation during initialization

    a convenient way to construct code.  writing this kind of
    assignment methods must be automated.


this is long already, i'll stop here.  any thoughts?  am i making sense?

rainer