Beefy Boxes and Bandwidth Generously Provided by pair Networks
Perl: the Markov chain saw

comment on

( #3333=superdoc: print w/replies, xml ) Need Help??
I think it's likely this technique would also work for you.

In fact, more than just likely...

sub from (&$) { use Devel::Callsite qw< callsite context >; use Scope::Upper qw< reap UP >; my ($iterator_source) = @_; # Uniquely identify this call, according to its lexical context... my $ID = callsite() . context(); # Install the iterator... state %iterator_for; $iterator_for{$ID} //= $iterator_source->(); # Install destructor for iterator at end of caller's block... reap { delete $iterator_for{$ID} } UP UP; # Iterate... return $iterator_for{$ID}->($_[1]); } for my $limit (reverse 1..5) { while ( from{countdown($limit)} my $a ) { print "$a: "; } print "\n"; } sub countdown{ my $val = shift; my $iter = sub { if ($val--) { $_[0]=$val; return 1; } return; # stop iteration }; return $iter; }

In reply to Re^5: Can I check if a loop's scope is entered for the first time? (Devel::Callsite) by TheDamian
in thread Can I check if a loop's scope is entered for the first time? by LanX

Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post; it's "PerlMonks-approved HTML":

  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.
  • Log In?

    What's my password?
    Create A New User
    and the web crawler heard nothing...

    How do I use this? | Other CB clients
    Other Users?
    Others meditating upon the Monastery: (8)
    As of 2021-01-26 13:15 GMT
    Find Nodes?
      Voting Booth?