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Path: utzoo!linus!vaxine!wjh12!harvard!mark
From: mark@harvard.UUCP (Mark Lentczner)
Newsgroups: net.lang
Subject: Re: Time for keyword parameters in prog. langs
Message-ID: <214@harvard.UUCP>
Date: Tue, 10-Apr-84 09:40:55 EST
Article-I.D.: harvard.214
Posted: Tue Apr 10 09:40:55 1984
Date-Received: Wed, 11-Apr-84 01:51:20 EST
References: <3781@utcsrgv.UUCP>
Organization: Aiken Computation Lab, Harvard
Lines: 39

-=-
    The SmallTalk-80 equivelent of `function calls' are based on
a form of keyword parameters.  When a message (roughly similar to
a function call) is passed the parameters (including the reciever
of the message) are each preceded by a keyword.  For example:
	rotate: car-object about: x-axis by: 45.0

    On the otherhand, SmallTalk-80 does not allow for the relative
positions of the keywords to change, in other words the message:
	rotate: car-object by: 45.0 about: x-axis
is actually a different message.  Despite this, I think that
SmallTalk-80 model gives a nice place for departure in this realm.

    I myself am working on a language & environment, EAMES, that does
various forms of patteren matching to execute messages.
My hope is to achieve an even greater freedom via a loosening of the
one keyword per parameter constraint and a flexible default system.
Thus, all of the following would incurr the same action:
	rotate car-object by 45 degrees about x-axis.
	rotate car-object about x-axis 45 degrees.
	about x-axis rotate car-object (PI / 2.) radians.
and allow the following to invoke similar actions (via defaults):
	rotate car-object PI radians.
	rotate car-object about y-axis.

    I would be interested in discussion and/or info & pointers on
other programming environments that have take other than the strict
"Macro-Expansion" approach to fitting action invocations with action
definitions.

- Mark Lentczner
  Harvard Electronic Music Studio
  Music Department
  Harvard University
  Cambridge, MA 01238

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