Re: Re: do/redo or for(;;): what's Kosher?

[merlyn]

That would be fine, except last/next/redo don't respect that as a "loop" because that's not a real loop-block. That's why I came up with the other version: it's a lean, mean, looping machine!

-- Randal L. Schwartz, Perl hacker

[dmmiller2k]

Just curious. Why would you prefer this:

{
   # do stuff
   last if BREAK-CONDITION;
   redo;
}

to this:

{
   # do stuff
   redo if !BREAK-CONDITION;
}

or even (just to be pedantic),

{
   # do stuff
   redo unless BREAK-CONDITION;
}

dmm

[tye]

I'm pretty sure that the reason is:

{
   # do loop stuff to be done at least once
   last if BREAK-CONDITION;
   # do middle loop stuff  <<< This part was left out
   redo;
}

which I'd still use while(1) for. Plus it allows you to do:

{
    # read next line
    last if NoMoreLines
    # extract item from line
    redo if NoItemInLine
    last if EndOfItemListFound
    # categorize item
    redo if WrongItemCategory
    # check for updates
    redo if NoUpdatesThisCategory;
    # check permissions
    last if NoUpdatesAllowed;
    redo if ThisUpdateNotAllowed;
    # do update
    redo if NotFatal;
    # handle fatal error
    # (note, no "redo" here so this part isn't really
    #  part of the "loop", just stuff to do once unless
    #  "last" gets triggered above.)
}
# done with items

where it is very easy to throw in a new check or new code in. But, as I said elsewhere, I find that power to be too easy to abuse. YMMV.
        - tye (but my friends call me "Tye")

[dmmiller2k]

Ah, in that context, I see where this approach could be useful.

I think I agree with you, though, that the while (1) (with scattered nexts in place of redos) accomplishes the same thing in a more self-explanatory way.

dmm

You can give a man a fish and feed him for a day ...
Or, you can teach him to fish and feed him for a lifetime