POE and $_[KERNEL]

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

I have started to take a hard look at POE, using merlyn's excellent Column 41 as a learning tool.

I'm making progress, but part of the Perl syntax has me confused. Specifically, in one routine merlyn gets the kernel object using my $kernel = $_[KERNEL]; (Line 38) and then uses it with $kernel->yield("ready", "looping"); (Line 48) which is fine, except I'm not familiar with this use of $_.

Later on in the example, in another routine, he skips that nicety and just says $_[KERNEL]->yield("ready", "child done"); (line 65). I'm familiar with @_, but I'm unsure about where $_ comes from in that context.

Can someone elighten me? Thanks.

Alex / talexb / Toronto

"Groklaw is the open-source mentality applied to legal research" ~ Linus Torvalds

Update 1: Fixed broken link; thanks zentara

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Re: POE and $_[KERNEL] by gellyfish (Monsignor) on Sep 06, 2005 at 18:00 UTC
The `$_[KERNEL]` is just an indexed access to `@_` using the predefined constant `KERNEL` - using the constants like this allows for one thing POE to not have to document explicitly the order in which all of the arguments are passed to the method. Update: frodo72 pointed me to http://poe.perl.org/?POE_FAQ/calling_convention that explains this rather nicely. /J\	[reply] [d/l] [select]
Re^2: POE and $_[KERNEL] by talexb (Chancellor) on Sep 06, 2005 at 18:04 UTC
D'Oh! Of course, `$_[some index here]` is just Perl accessing the `@_` array. And I already know that `KERNEL` is a constant -- defined as a simple function in POE::Session. Sorry, that was a somewhat lame question -- for some reason I thought it was doing some wonderfully dark magic that wasn't even in the Camel. Phew. Alex / talexb / Toronto "Groklaw is the open-source mentality applied to legal research" ~ Linus Torvalds	[reply] [d/l] [select]
Re: POE and $_[KERNEL] by zentara (Cardinal) on Sep 07, 2005 at 09:47 UTC
I think your link to Merlyn's Column 41 is broken. It needs an href not an [id:// I'm not really a human, but I play one on earth. flash japh	[reply]