Front page | perl.perl5.porters |
Postings from October 2003
On Wed, Oct 08, 2003 at 03:47:35PM -0500, Johnson, Roy wrote: > defined() should evaluate its arguments in a context [I'm using this > term generically] wherein only undef is false. The normal usage of > defined() is unchanged: if you give it an undef value, it returns false, > otherwise, it returns true. However, if you give it a complex Boolean > argument, all of the logical operators recognize undef as false, and > everything else as true, and logical operators yield undef instead of > normal-perl-false. > > Examples: > defined($v = a() || b()) ## equivalent to $v = a() // b(); > defined($v ||= a()) ## equivalent to $v //= a(); > defined($v = \( $a && $b && $c && 'full')) Seems like an awfully complex hack for something that's already been rather handily fixed. > No new keywords or operators are required for this behavior. It is > straightforward This doesn't strike me as straightforward at all. In fact, its rather hackish to have an expression behave so differently as an argument to a function. > and provides access to all logical operations, rather > than being specific to two. There's been little call for "defined-and" or "exists-or" operators. > Disadvantages: > It still does not make it easier to do something like: > $a = a() // b() || c() // d(); > which would be (as it currently is): > defined($a = a()) || ($a = b()) || defined($a = c()) || ($a = d()); A fairly major disadvantage. That second one is pretty ugly. > "defined" is still a relatively long word Another disadvantage is it complicates defined() and exists() in a way that's fairly difficult to explain. dor is easy to explain "its like or except it checks for just definedness instead of truth". Finally, this looks like it would be a bitch to implement.Thread Previous