Re: I don't understand this grep

The following code

sub channels_by_level { grep { $_[0]->level( $_[1] ) } $_[0]->channels
+ }
[download]

can be written more clear such as:

sub channels_by_level { 
    my $self  = shift;
    my $level = shift;
    return grep { $self->level( $level ) } $self->channels;
}
[download]

Method $obj->channels_by_level($level) returns those channels which has level given in an argument.

The problem is that your object doesn't have channels. To understand why it doesn't more code need to be shown.

Comment on Re: I don't understand this grep Select or Download Code

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Re^2: I don't understand this grep by gone2015 (Deacon) on Nov 05, 2008 at 18:07 UTC
The curious thing is that the test in the `grep`: `return grep { $self->level( $level ) } $self->channels;` [download] contains nothing that depends on whatever $self->channels is or returns. It could equally be written: `return $self->level($level) ? $self->channels : () ;` [download] but that doesn't answer the question of why `$self->channels` appears to be missing.	[reply] [d/l] [select]
Re^3: I don't understand this grep by ikegami (Patriarch) on Nov 05, 2008 at 18:50 UTC
I wonder if it's supposed to be `return grep { $_->level( $level ) } $self->channels;` [download]	[reply] [d/l]
Re^4: I don't understand this grep by ccn (Vicar) on Nov 05, 2008 at 19:17 UTC
Yes it's easy to mess `$_` and `$_[0]`. Nobody see that until an error occured.	[reply] [d/l] [select]
Re^4: I don't understand this grep by gwhite (Friar) on Nov 05, 2008 at 19:25 UTC
I tried adjusting the syntax and got the exact same message. $self->channels is not defined anywhere in the module, so it is either misnamed or missing. I will have to figure that out g_White	[reply]
Re^3: I don't understand this grep by gwadej (Chaplain) on Nov 05, 2008 at 18:11 UTC
~~Well, that won't work if `$self->channels` returns a list, which seems likely, based on the name.~~ Update: Need to engage eyeballs before fingers. Thanks massa and jwkrahn for an appropriate whack on the side of the head. G. Wade	[reply] [d/l]
Re^4: I don't understand this grep by jwkrahn (Abbot) on Nov 05, 2008 at 18:37 UTC
That should work fine. What makes you think that it won't work?	[reply]
Re^4: I don't understand this grep by massa (Hermit) on Nov 05, 2008 at 19:00 UTC
??!!! Yes it will work with `channels` returning a list, according to Conditional operator: Scalar or list context propagates downward into the 2nd or 3rd argument, whichever is selected. *And* it won't execute `$self->level($level)` once for each item of the returned list, which is good. Now, the reason why `channels` is missing is because... well, gwhite didn't show any `sub channels { ... }` in the module... But he didn't state that it does not exist, either... []s, HTH, Massa (κς,πμ,πλ)	[reply] [d/l] [select]
Re^5: I don't understand this grep by gwhite (Friar) on Nov 05, 2008 at 19:21 UTC
Re^5: I don't understand this grep by gwadej (Chaplain) on Nov 05, 2008 at 19:28 UTC


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