>>>>> "MGS" == Michael G Schwern <Michael> writes:
MGS> You've seen Mark Lentczner's Periodic Table of Perl 6 Operators MGS> http://www.ozonehouse.com/mark/blog/code/PeriodicTable.html MGS> What about one for Perl 5? MGS> http://www.pobox.com/~schwern/tmp/perl5ops MGS> So... did I miss anything? "and" and "or" are the only ones that jump out at me. I think they definitely deserve their own entries: subjectively, I'd say "&&" is more different from "and" than "," is from "=>" or than """" is from "qq//". MGS> The big step is to work out operator precedence. perlop has a 24 MGS> level precedence table but I suspect that's perhaps the biggest MGS> white lie in all the Perl docs. Can Perl 5 even be said to have MGS> a simple enough idea of op precedence to apply a number to each MGS> op? If so, how does one go about figuring this out? I think perlop's table covers it pretty well. Precedence doesn't really make sense for "circumfix" things like parentheses and quotes, but it's pretty well defined for prefix, infix, and postfix operators. For function-like operators, you consider the case where they're operating on exactly one argument. In general, you test the precedence between two operators by setting up a fight and seeing which one wins. In the classic infix-infix case, for instance, if you want to see whether + or * has higher precedence, you write: 1 + 2 * 3 and see whether the answer is 9 or 7. The other combinations you can test are PREFIX arg INFIX arg arg INFIX arg POSTFIX and PREFIX arg POSTFIX Even if you can't think of an example that makes semantic sense, you can often use -MO=Deparse,-p to see how Perl is doing its parsing. For instance, to see that the precedence of "-r" is in between that of ">" and that of ">", say: % perl -MO=Deparse,-p -e '-r $x >> $y' -r(($x >> $y)); # >> wins % perl -MO=Deparse,-p -e '-r $x > $y' (-r($x) > $y); # -r wins I've correlated your list with the levels used in B::Deparse (based on perlop) here: http://www.csua.berkeley.edu/~smcc/p5p-tmp/perl5ops-prec -- Stephen
