in reply to An iterator for (not "iterating") a recursive data structure.

There is the simple "flatten as you go" approach:


sub genIterator
  { 
  my @stack = @_;
  return sub 
    {
    splice @stack, 0, 1, @{$stack[0]} while 'ARRAY' eq ref $stack[0];
    shift @stack;
    }
  }

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Re^2: An iterator for (not "iterating") a recursive data structure.
by BrowserUk (Patriarch) on Feb 14, 2015 at 23:02 UTC

    S'fine for small AoAoA..s, but the top level array in my application will contain upto 200 million elements -- circa. 7GB -- duplicating that on a stack would blow my memory.

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[reply]
      > duplicating that on a stack would blow my memory.

      It's not duplicating the memory, just caching the current path from root to leave, very similar to my solution here

      Worst case scenario with a balanced two level "tree" would mean approx @stack == 2*sqrt(@nodes) .

      For 200 million elements that's about 28000 elements.

      If that's still to many store a lazy iterator in the @stack returning the children of one node (like a function ref or an object or a tied array) and process it in the iterator.

      Cheers Rolf
      (addicted to the Perl Programming Language :)
      Wikisyntax for the Monastery FootballPerl is like chess, only without the dice

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