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Re^4: Need help figuring out how to order/eval the numbers

by aaron_baugher (Curate)
on Jun 22, 2015 at 23:59 UTC ( #1131546=note: print w/replies, xml ) Need Help??


in reply to Re^3: Need help figuring out how to order/eval the numbers
in thread Need help figuring out how to order/eval the numbers

That's not error checking. His comment meant that you should add error checking there, to make sure the values being compared exist and are numbers, for instance.

The <=> operator (search for it in perlop) compares two numbers and returns -1 if the left argument is less than the right one, 0 if they are equal, and +1 if the left argument is greater than the right. It's very commonly used in sort routines, since sort then uses those -1/0/+1 return values to decide which of two values should come first. The way sort works (simplistic explanation coming) is by comparing values in the list to each other, two at a time, and swapping them if they're out of order, and continuing until the entire list is sorted. The subroutine or block you provide as the sort routine is what it uses to compare the two values, which are passed to that routine as $a and $b.

So he's having sort call sort_italian() to do the comparisons, and it uses the <=> operator to compare the values numerically.

Aaron B.
Available for small or large Perl jobs and *nix system administration; see my home node.

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Re^5: Need help figuring out how to order/eval the numbers
by perlynewby (Beadle) on Jun 23, 2015 at 01:52 UTC

    Ahh, Thank you Aaron for your well explained comments/insights.

    darn, I couldn't find a section to read about the <=> thingy...In fact, I didn't know what to look for...I'm too new to know what that means or search for that thingy in my book I got from library.

    reading on this tonight so tomorrow may have more questions

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