in reply to Control Flow Puzzle

I tend to break these down to a naked block: 
{
  $_ = <INFO>;
  return %Header unless defined $_ and !/^\037/;
  last if /^\* Menu:/;
  redo;
}

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And as I'm writing this, I'm wondering if something belongs between the last and redo lines there. What are you doing for non 37, non menu lines? Just skipping them?

-- Randal L. Schwartz, Perl hacker

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RE: Control Flow Puzzle
by Dominus (Parson) on Nov 16, 2000 at 02:34 UTC
    Randal said: 
    {
   $_ = <INFO>;
   return %Header unless defined $_ and !/^\037/;
   last if /^\* Menu:/;
   redo;
}

    [download]
    That's really interesting. Why do you prefer that to this: 
    while (1) {
   $_ = <INFO>;
   return %Header unless defined $_ and !/^\037/;
   last if /^\* Menu:/;
}

    [download]
    This seems the same to me, only less abnormal.

    > What are you doing for non 37, non menu lines? Just skipping them?
    Yes, exactly so. The 37 line marks the end of the 'node'. If the function sees a 'menu' line before the 37 line, it knows that the node contains a menu, and the following code processes the menu up to the following 37 line. Lines that look different are not of interest to this function.

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      Why the naked block instead of the infinite loop? Style thing, I guess. Over time, I usually end up hacking the naked block, adding and deleting conditions of restart and exit. The naked block has cleaner semantics for me, going up only when and where I tell it, and falling out otherwise. Certainly for this case I could have switched to an infinite loop once I saw that the form fits, but I don't know that when I first start, and I consider a naked block to be a more primitive form. {grin}

      -- Randal L. Schwartz, Perl hacker

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      What about a loop-less solution? 

      undef $/;
$_=<>;
s/(\n\037.*?\n\* Menu.*?\n\037)//;
$mymenu=$1;

      [download]
      This way you put all input into one string, and just pick out the menus one by one. No tricky loops anymore. I don't know how much you rely on the markers to start at the beginning of the line, but you could remove the newlines in the regex, of course.

      I pray I didn't say something very stupid here. Please excuse me if this is the case..... And credits to little, who only yesterday showed me the undef $/ trick.

      Cheers,

      Jeroen

      Post Posting: Mr. Schwartz, `Learning perl' was my first contact with perl, and I really loved it, and enjoyed reading it very much! So, thanks a lot...

      I was dreaming of guitarnotes that would irritate an executive kind of guy (FZ)

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