Re: <boolean> <true> & <false>

[eliot@dcs.qmw.ac.uk]

>
>>   ...If you have separate classes for true & false then its possible
>>   to define the basic control structures using polymorphism on #t &
>>   #f and lambda (method)....
>
>While this is a simplification in theory, I don't think it would simplify
>the practice of programming in Dylan.  It might be different in Self and
>Smalltalk.
>
>If you allow the user to define methods on IF, then it also makes things
>much harder for the compiler.
>
>   -Andrew
>
I'm not sugesting one replace the IF special form by methods.  The
compiler can in-line the Smalltalk-style methods/lambda version of IF, but then
debugging the code reveals that the compiler has treated the IF message
specially.  So if one is concerned about efficiency then use hard-wired control
structures.  

My feeling is that if you introduce a class <boolean> which allows
you to specialise methods on <boolean> and non-<boolean> you should introduce
<true> & <false>, since its likely you will want to specialise methods on
<true> & <false>.

-- 
Eliot Miranda,  Lecturer	email:	eliot@dcs.qmw.ac.uk
Department of Computer Science	ARPA:	eliot%dcs.qmw.ac.uk@nsf.ac.uk
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