André Thieme wrote:
> [EMAIL PROTECTED] schrieb:
> William James schrieb:
> >>> How would you solve this in Python?
> >>> You could embed it inside a lambda and must somehow make the
> >>> variable "it" visible in it, because in the context of aif this
> >>> "it" gets bound to the result.In Ruby:
> >> def aif val
> >> yield val if val
> >> end
> >>
> >> def complex_calc n
> >> if n % 2 == 1
> >> n**n
> >> else
> >> nil
> >> end
> >> end
> >>
> >> aif( complex_calc( 9 ) ) {|x| puts "hello, #{x}"}
> >> aif( complex_calc( 8 ) ) {|x| puts "hello, #{x}"}
> >>
> >> --- output -----
> >> hello, 387420489
> >>
> > Okay, so it's certainly _doable_. I think the question is more if it's
> > usable. Regular if:s don't like that in Ruby/Python/similar, and adding
> > such a construct would mean extending the syntax.
> >
> > In Lisp, all (well, almost) functions are equal, so an (if ...) would
> > look the same like the (aif ...). I think that's the point here.
>
> Exactly that is the point.
> *Of course* it is doable.
> And what William shows us is maybe one of the best solutions
> in Ruby. He used advanced abstractions that made it possible.
> The thing with most (if not all) programming languages other than Lisp
> is: these abstractions are leaky.
> They have a low level knowledge leak. Users of aif need to know how to
> pass in arguments. As you see he had do embed the code that needs execution
> into a block (anon function) and then use this special syntax for x.
>
>
> André
> --
I may have tried too hard. The simpler way is usually better.
No aif() is needed:
if x = complex_calc( 9 )
puts "hello, #{x}"
end
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