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Re^3: fibonacci numbers using subroutine?

by TimToady (Parson)
on Aug 20, 2010 at 18:33 UTC ( #856341=note: print w/replies, xml ) Need Help??


in reply to Re^2: fibonacci numbers using subroutine?
in thread fibonacci numbers using subroutine?

In practice, though, if you're going to reuse a series in your Perl 6 program, you'll want to memoize the series by binding the series to an array, like this:
my @fib := (0,1, *+* ... *); say @fib[8]; say @fib[9]; # doesn't recalculate fib(8)
Both lists and arrays can be lazily infinite in Perl 6; the only real difference is whether the values are kept in an indexable form as they are generated. Note also that the memoization naturally uses an array rather than a hash in this case, which saves memory over those memoization techniques that must assume a hash for generality.

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[Corion]: hippo: If you have a Unicode-wise Perl then likely some zero-width characters in $x would work. Maybe $x = "\x{200b}" works.
[Corion]: Hmm - no, that outputs 1 for me on 5.14 - perl -wle "my $x = qq(\x{200b}); warn $x; warn length $x"
[hippo]: Smart - I'll give that a go. Thanks.
[hippo]: Ah
[Corion]: But maybe there is some other Unicode string that will be true but have a zero width
[hippo]: For explanation, I've seen this construct in someone else's code (no names, no pack drill) and couldn't think of a situation to trigger it.
[Corion]: You'll have to look somewhere esoteric for that. Maybe some tied variable or special dualvar can also trigger that. But it's certainly not a common occurrence
[Corion]: And on 5.20, the following also outputs no find:perl -wle 'for my $x ("\x{2000}".."\ x{1fffff}") { if( $x && ! length $x ) { warn qq(<$x>); warn length $x; die } }'
[Corion]: (this time on Unix)

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