Re: Does Combinator.'or' miss then-statements?

Sun, 04 May 2008 09:49:45 -0700 

OK, done

Best
Torsten

On May 4, 2008, at 5:08 PM, Raphael Collet wrote:


Dear Torsten,
That would be really nice to add such a comment. I even suggest to use 
a mixture of both, which shows all possible cases:

    or S1
    [] S2
    [] S3 then S3
    end

expands to something like

    local
       proc {C1} S1 end
       proc {C2} S2 end
       fun {C3} S3 proc {$} S4 end end
    in
       {Combinator.'or' C1#C2#C3}
    end

Thanks a lot,
raph

Torsten Anders wrote:


Dear Raphael,

thanks for your reply. Is it OK if I add the following to the doc of
Combinator.'or'?

Best
Torsten


-- doc proposal


  {Combinator.'or' +T}

implements disjunction. T is a tuple of either nullary or unary
procedures. The special syntax statement

  or S1 [] S2 [] S3 end

expands to
{Combinator.'or' proc {$} S1 end # proc {$} S2 end # proc {$} S3 end} 

whereas

  or S1 then S2
  [] S3 then S4
  end

expands to the following

local
    fun {C1} S1 proc {$} S2 end end
    fun {C3} S3 proc {$} S4 end end
in
    {Combinator.'or' C1#C2}
end


--



On May 4, 2008, at 3:22 PM, Raphael Collet wrote:


Dear Torsten,
I agree with you, these combinators definitely lack documentation. But here is how I found a solution to your problem: I simply looked at the 
'Core Syntax' of you guarded or-statement:


or X=1 then Y=11
[] X=2 then Y=12
[] X=3 then Y=13
end


The statement is equivalent to

local
    fun {C1} X=1 proc {$} Y=11 end end
    fun {C2} X=2 proc {$} Y=12 end end
    fun {C3} X=3 proc {$} Y=14 end end
in
    {Combinator.'or' C1#C2#C3}
end
Now we can infer the rule: a guarded clause "A then B" is encapsulated in a function that executes A and returns a procedure that encapsulates 
B.  In other words: fun {$} A (proc {$} B end) end.
I also checked the implementation of the combinator (its source code is in the file share/lib/cp/Combinator.oz), and the rule above is correct. 

Cheers,
raph
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--
Torsten Anders
Interdisciplinary Centre for Computer Music Research
University of Plymouth
Office: +44-1752-586227
Private: +44-1752-558917
http://strasheela.sourceforge.net
http://www.torsten-anders.de
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--
Torsten Anders
Interdisciplinary Centre for Computer Music Research
University of Plymouth
Office: +44-1752-586227
Private: +44-1752-558917
http://strasheela.sourceforge.net
http://www.torsten-anders.de





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