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Re: why tail recursion matters and why Java isn't it, was Re: lispperformance was Re: problems with lisp

Shriram Krishnamurthi wrote:
> Pascal Costanza <costanza@iai.uni-bonn.de> asks in what I can only
> hope is a fit of passion overcoming rational thought:
>>Why should it be important to cover all cases? 
> Because programming language designers should not think they are a
> whole lot smarter than the programmers who will use their language.
> (Note: This wording even accommodates the design of Arc.)

I totally agree. Are language designers who don't include loop 
constructs in a language a "whole lot smarter" than the programmers who 
will use their language?

> Pushing even further, I would not want to use a programming language
> that *prohibits* the creation of syntactic abstractions that better
> capture constructs for a particular domain, especially new binding
> constructs and control structures ("loops").  While the language no
> doubt already supports pretty useful constructs for many purposes, I
> would not want a barrier to creating a better lightweight embedded
> language.  A good language provides macros or templates just so it can
> "cover all cases".

I don't see how this contradicts my view. I totally agree with your 
statements but I don't see how they preclude looping constructs in a 

Yes, loop in Common Lisp is not extensible, and this is a disadvantage. 
But I am not arguing that Common Lisp provides the best possible 
solution in this regard.

> Now in any other context, I would imagine that it would be you, the
> Common Lisp fan, making precisely this set of cases.  So when did
> covering all cases cease to be an objective of a general purpose
> language?  And if you buy into the above, then tail calls become
> inevitable; a macro system without tail calls underneath is
> fundamentally hobbled.

Yes, I am a Common Lisp fan, but this doesn't matter much for the topic 
at hand.

Yes, Common Lisp with proper tail recursion and call/cc would be a 
better language.


Pascal Costanza               University of Bonn
mailto:costanza@web.de        Institute of Computer Science III
http://www.pascalcostanza.de  Römerstr. 164, D-53117 Bonn (Germany)