Re^2: Line numbers

in reply to Re: Line numbers
in thread Line numbers

is there any advantage of [caller(0)]->[2] over (caller(0))[2]?

Cheers Rolf

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Re^3: Line numbers by tobyink (Canon) on Mar 16, 2012 at 23:33 UTC
Indeed there is an advantage of the first - I can remember the syntax. It is non-obvious why `(caller(0))[2]` should work but `caller(0)[2]` should fail. Also, the arrayref plays nicer associativity wise. Check this out: `$ perl -E'sub x { say [caller(0)]->[0] } x()' main $ perl -E'sub x { say (caller(0))[0] } x()' syntax error at -e line 1, near ")[" Execution of -e aborted due to compilation errors.` [download] The version with the arrayref just acts more predictably in my mind. I don't have to waste time thinking about it. `perl -E'sub Monkey::do{say$_,for@_,do{($monkey=[caller(0)]->[3])=~s{::}{ }and$monkey}}"Monkey say"->Monkey::do'`	[reply] [d/l] [select]
Re^4: Line numbers by chromatic (Archbishop) on Mar 17, 2012 at 00:02 UTC
It is non-obvious why `(caller(0))[2]` should work but `caller(0)[2]` should fail. Precedence.	[reply] [d/l] [select]
Re^5: Line numbers by tobyink (Canon) on Mar 17, 2012 at 00:12 UTC
That there exists an explanation does not imply that the explanation is obvious. I understand that light may act as a wave or particle depending on how you study it. However, this fact is not obvious. It is in fact incredibly non-obvious, which is how it took science so long to get there. That `[caller(0)]->[0]` works is (at least to me) obvious. That `(caller(0))[0]` works and `caller(0)[0]` fails is (again, to me) non-obvious. `perl -E'sub Monkey::do{say$_,for@_,do{($monkey=[caller(0)]->[3])=~s{::}{ }and$monkey}}"Monkey say"->Monkey::do'`	[reply] [d/l] [select]
Re^6: Line numbers by chromatic (Archbishop) on Mar 17, 2012 at 00:42 UTC
Re^6: Line numbers by Anonymous Monk on Mar 17, 2012 at 00:39 UTC
Re^7: Line numbers by LanX (Saint) on Mar 17, 2012 at 01:57 UTC
Re^5: Line numbers by LanX (Saint) on Mar 17, 2012 at 00:07 UTC
Well he rather meant "intuitive", all examples are about precedence. Cheers Rolf	[reply]
Re^5: Line numbers by gg48gg (Sexton) on Mar 17, 2012 at 01:46 UTC
Right. The added complexity actually comes from introducing the say function, which takes a list. `say (caller(0))[0];` [download] is expanding to: `say $package, $filename, $line, $subroutine, $hasargs,$wantarray, $eva +ltext, $is_require, $hints, $bitmask, $hinthash,[0];` [download] This gives you the syntax error: `say [0];` [download]	[reply] [d/l] [select]
Re^6: Line numbers by LanX (Saint) on Mar 17, 2012 at 02:04 UTC
Re^7: Line numbers by gg48gg (Sexton) on Mar 19, 2012 at 17:42 UTC
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Re^6: Line numbers by Anonymous Monk on Mar 17, 2012 at 02:10 UTC
Re^4: Line numbers by LanX (Saint) on Mar 17, 2012 at 00:08 UTC
Thanks! Personally I don't like referencing for immediate dereferencing. But that's a matter of taste... Anyway I'd rather prefer a clean named argument solution instead of those silly positional parameters of caller. Cheers Rolf	[reply]
Re^5: Line numbers by repellent (Priest) on Mar 17, 2012 at 06:51 UTC
Anyway I'd rather prefer a clean named argument solution instead of those silly positional parameters of caller. Devel::StackTrace	[reply]

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