sorting objects

Anonymous Monk has asked for the wisdom of the Perl Monks concerning the following question:

what's wrong with this code :

actually two questions :

1) why don't the $a,$b values of the SORT routine
print ?

2) what is wrong with the sort routine?
it doesn't sort; (rearrange the list)

package netFetObj;
sub fetSort {
print " ######### A = $a \n";
print " ######### B = $b \n";
    my $ftA = $a->{"fet"};
    my $ftB = $b->{"fet"};
    $fetType->{$ftA} <=> $fetType->{$ftB}
}
[download]

where fetType is updated
whenever the appropriate object method is invoked

package something_else;
    foreach my $fetOBJ ( sort { &netFetObj::fetSort } @{ $OBJ->{"fets"
+} } ) {
        buildFet($FH,$fetOBJ,$OPT);
    }
[download]

and the LIST to sort is a list of netFetObjs.

Edited by planetscape - removed pre tags, added code tags and rudimentary formatting

( keep:0 edit:6 reap:0 )

Comment on sorting objects Select or Download Code

Replies are listed 'Best First'.
Re: sorting objects by rhesa (Vicar) on Jun 23, 2006 at 01:16 UTC
Two notes: sort can take a subname, so a simple `sort netFetObj::fetSort @list` looks cleaner than your construct. if you don't use a prototyped sort sub, `$a` and `$b` are globals in package `something_else`. That means you should refer to them as `$something_else::a` and `$something_else::b` inside `fetSort`. To summarize: `package netFetObj; sub fetSort { print " ######### A = $something_else::a \n"; print " ######### B = $something_else::b \n"; my $ftA = $something_else::a->{"fet"}; my $ftB = $something_else::b->{"fet"}; $fetType->{$ftA} <=> $fetType->{$ftB} } package something_else; foreach my $fetOBJ ( sort netFetObj::fetSort @{ $OBJ->{"fets"} } ) + { buildFet($FH,$fetOBJ,$OPT); }` [download]	[reply] [d/l] [select]
Re^2: sorting objects by Anonymous Monk on Jun 23, 2006 at 01:33 UTC
doh! i feel really silly. of course, the variables would be in the namespace of the caller. i had tried various combinations of & and $ on the sort routine. little did i realize that NO symbols are needed! yes, i need to use a prototyped sort sub as many other packages will call this. BTW, i also changed the hash access to a method `my $ftA = $_[0]->fet(); my $ftB = $_[1]->fet();` [download] this looks cleaner too! thanks again... Formatting and code tags added by GrandFather	[reply] [d/l]
Re: sorting objects by ikegami (Patriarch) on Jun 23, 2006 at 01:16 UTC
`sort` is placing the values in `$something_else::a` and `$something_else::b` since it was called from package `something_else`. The workaround is to tell `sort` to pass the values as parameters by using the `($$)` prototype: `sub fetSort($$) { # Prototype necessary. my $ftA = $_[0]->{"fet"}; my $ftB = $_[1]->{"fet"}; $fetType->{$ftA} <=> $fetType->{$ftB} } package something_else; sort netFetObj::fetSort @{ $OBJ->{"fets"} }` [download] This negatively affects performance, according to the docs. In the future, please use `<c>...</c>` around your code rather than (an unclosed) `<pre>...</pre>`, as per the Monestary Guidelines. A janitor will have to fix it for you.	[reply] [d/l] [select]