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Postings from July 2010
On Wed, Jul 28, 2010 at 11:58, Nicholas Clark <nick@ccl4.org> wrote: snip > If you're up for it, I don't think that it's documented anywhere that the > false value returned by a logical operator is a special case: > > $ perl -wle '$a = 0 == 1; print ">$a<"; print $a + 0' >>< > 0 > > it is both the empty string, and a numeric zero. > (That's not a special case in any conversion code. It's a dual value) snip Yeah, I missed that when I documented the relational and equality operators in perlopquick. I will go back and add that detail to them. snip > Also, $! is a dual value, with the string value being the error string, and > numeric value being the error code. On this system, the error string for 0 > *is* an empty string, hence this is false: > > $ perl -wle '$! = 0; print ">$!<"; print $! + 0' >>< > 0 snip I think that is fairly well documented in perlvar. snip > And if you're really up for it, there's a bug with no obvious fix if your > system supports negative zero: > > $ perl -wle '$a = 0/-1; print $a ? "T" : "F"; print $a; print $a ? "T" : "F";' > F > -0 > T snip That only happens on one's complement machines right? Are there any one's complement machines left? -- Chas. Owens wonkden.net The most important skill a programmer can have is the ability to read.Thread Previous | Thread Next