On Oct 19, 2004, at 08:50, Jason Foster wrote:
Can anyone help me to understand why this code refuses to compile? Even better, can anyone help fix it :)
%hash = qw( fred filntstone barney rubble tom delong ); print( keys( reverse( %hash ) ) );
The error message...
Type of arg 1 to keys must be hash (not reverse) at ./killme.pl line 4, near ") ) "
... was pretty confusing since it implies that "reverse" is a type?!
$ perldoc -f keys
keys HASH
...
$ perldoc -f reverse
reverse LIST
In list context, returns a list value consisting of the ele-
ments of LIST in the opposite order. In scalar context, con-
catenates the elements of LIST and returns a string value with
all characters in the opposite order.
reverse returns a list. keys expects a hash.
Reversing a hash doesn't make sense, assuming you're thinking of reverse in the same sense as a list. The members of a hash are not stored in the order in which they were inserted; if you iterate a hash, the order in which you visit members is dependent only on the implementation of the hash. In other words, if order is important to you, don't use a hash.
On the other hand, you can *invert* the hash, swapping keys with values. I think that's in the perlfaq.
-1 for fun.
-- Craig S. Cottingham [EMAIL PROTECTED] OpenPGP key available from: http://pgp.mit.edu:11371/pks/lookup?op=get&search=0x7977F79C
