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Re: Mini HowTo: How to port Perl 5 modules to Perl 6

by webfiend (Vicar)
on Mar 25, 2005 at 20:55 UTC ( #442408=note: print w/ replies, xml ) Need Help??


in reply to Mini HowTo: How to port Perl 5 modules to Perl 6

Very nicely put together. I had to read this twice, though. Once for the "Aaagh! So many changes. What are they doing to the grep/map chain? How are those accessors better? Waah!" Then once more, a few minutes later, to recognize how much cleaner this will make a lot of my Perl code. Now I'm all excited again!


Comment on Re: Mini HowTo: How to port Perl 5 modules to Perl 6
Re^2: Mini HowTo: How to port Perl 5 modules to Perl 6
by iblech (Friar) on Mar 25, 2005 at 21:29 UTC

    The old grep/map/sort chain works unmodified, too, I just wanted to demonstrate the new pipeline operators. Actually, there are even some other ways too:

    # Perl 5: print join "...", map {...} sort {...} @array; # Perl 6: say (@array.sort:{...} ==> map {...}).join("...");

    TIMTOWTDI :)

    The accessors are especially useful for subclassing:

    class Foo { has $.x; # Explicitly generate an accessor: method x() is rw { return new Proxy: FETCH => {...}, STORE => {...}; } } class Foo::Bar isa Foo { method do_sth { ...; my $var = $.x; # Although used as an variable, the *method* Foo.x is called. # Foo::Bar does *not* directly access the variable. } }

    Now, you may ask, "why is that useful?" -- In Perl 5, when one changed the internal representation of some data in the superclass, but fixed the public accessor methods so they translate between the old representation the user expects and the new one used internally, everything was fine. Except, when there was some subclass: The subclass would still directly access the internal representation, which would, of course, not work.

    Now, with Perl 6, one may subclass freely without having to fear that internal changes of the superclass will affect the subclass. :)

    Generally, the Perl 5 way works in Perl 6, too. But the new ways Perl 6 gives you are often shorter/clearer/more consice/more elegant/more efficient/whatever.

    --Ingo

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