Path: utzoo!attcan!uunet!cs.utexas.edu!rice!uw-beaver!uw-june!jmaloney
From: jmaloney@cs.washington.edu (John Maloney)
Newsgroups: comp.object
Subject: Re: Objective-C review
Message-ID: <12396@june.cs.washington.edu>
Date: 27 Jun 90 18:41:03 GMT
Organization: U of Washington, Computer Science, Seattle
Lines: 30

In reply to Brad Cox's statement:
> what about a C-based varient of Smalltalk Blocks?

I think that blocks (or "closures", to be technical) are an extremely
valuable language mechanism. They allow all sorts of customized control
structures to be synthesized without extending the language semantics at all.
For example, the Smalltalk-80 *language* has no control flow mechanisms
other than blocks. Everything else -- if-then-else, loops, iteration over
collections -- is implemented using blocks.

While we're wishing: I think that end-user customization is going to be
increasingly desirable, especially in user interfaces. That is, end-users
will increasingly write little mini-programs to tailor applications to their
precise needs. What language should they use to do this? Why not Smalltalk,
Objective-C, or Lisp -- i.e. the language of the base application? This obviates
the need for a custom language and its interpreter. In Smalltalk, it is quite
easy to compile a string typed by the user into a custom code fragment that
can be executed by the application at appropriate times. For example, the
user might customize the behavior of a button or add a new item to a menu.
What I'm suggesting is that programs like HyperCard would not need to
supply a "HyperTalk" language if they could use C++ or Objective-C as the
customization languague. Smalltalk and Lisp already allow this. It is harder
to achieve in the C-based OOP dialects because:
    a) the compiler is not usually part of the run-time system, and
    b) symbol table information needed for variable bindings is often
        removed during compilation.

I would thus like to add "dynamic compilation and binding" to the wish-list.

	-- John