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From: ericco@stew.ssl.berkeley.edu (Eric C. Olson)
Newsgroups: comp.lang.lisp,comp.lang.scheme
Subject: Re: Virtues of Lisp syntax
Summary: example, example, example
Message-ID: <1990Sep17.165305.12538@agate.berkeley.edu>
Date: 17 Sep 90 16:53:05 GMT
References: <3368@skye.ed.ac.uk> <1350030@otter.hpl.hp.com> <3408@skye.ed.ac.uk> <15089@yunexus.YorkU.CA>
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One way of evaluating the "virtues" of a language, is to compare their
expressiveness.  For example, someone already mentioned that an infix
notation parser can be readily added to Lisp.  I mentioned previously
that for ruled based expert systems, a lhs/rhs parser is also a simple
extention to Lisp.  Making a similiar system in an Algol language is
more complex.  Inorder for the rules to be expressed in the native
language the generated "meta" level code must be passed through the
compiler.  This may require system calls, or an inferior process, or
that the compiler be imbedded into program.  A good working example of
this is C++, which (typically) converts instructions into C code.

However there are significant limitations on what can be done in C++.
For example, suppose you need to convolve an image as quickly as
possible, and that the convolution kernel is not known at compile
time.  In Lisp, one can easily write code to make a function that applies
a specific convolution kernal to an image.  The generated code only
contains a single loop and a bunch of conditional statements for
boundaries, a sum, and a bunch of multiplications.  Almost
any modern Lisp compiler can generate efficient code for this.  In
addition, special case can be handled.  In particular, kernals with
zero values and ones can be optimized.

My impression is that writing a similiar piece of code in Algol
languages would be needlessly complicated (although doable).

I've also seen Lisp implementations in C, and C implementations in
Lisp.  Although I've seen more Lisp implementations in C, I rather
enjoyed using C in Lisp -- since it caught all my illegal pointers
during program development and safely returned the Lisp debugger.

Anyway, I've yet to find an application that can be easily implemented
in an Algol language that cannot be readily implemented in Lisp.
However, the above examples are easily implemented in Lisp, but, I
think, are not readily implemented in Algol languages.

But, hey, some one tell me I'm wrong.  I'll listen.
Eric

Eric
ericco@ssl.berkeley.edu