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Re: map a list - segfault

by imp (Priest)
on Mar 12, 2007 at 20:00 UTC ( #604422=note: print w/replies, xml ) Need Help??


in reply to map a list

The block that caused the segfault doesn't work the way you think it does, because of precedence:
perl -MO=Deparse -e ' (@n=(1,2) && ($n[1],$n[0])); (@n=(1,2) && ($n[1],$n[0])); (@n=(1,2) && ($n[1],$n[0])); ' @n = ('???', 2) && ($n[1], $n[0]); @n = ('???', 2) && ($n[1], $n[0]); @n = ('???', 2) && ($n[1], $n[0]);
Using 'and' instead of && would work, or an extra set of parens.
perl -MO=Deparse -e ' (@n=(1,2) && ($n[1],$n[0])); ((@n=(1,2)) && ($n[1],$n[0])); (@n=(1,2) and ($n[1],$n[0])); ' @n = ('???', 2) && ($n[1], $n[0]); $n[1], $n[0] if @n = (1, 2); $n[1], $n[0] if @n = (1, 2);

As for the segfault itself, I don't grok why it breaks but Devel::Peek gives a hint:

perl -MDevel::Peek -le ' (@n=(1,2) && ($n[1],$n[0])); print Dump \@n; (@n=(1,2) && ($n[1],$n[0])); print Dump \@n;' SV = RV(0x3c02b018) at 0x3c0062dc REFCNT = 1 FLAGS = (TEMP,ROK) RV = 0x3c011718 SV = PVAV(0x3c0084dc) at 0x3c011718 REFCNT = 2 FLAGS = () IV = 0 NV = 0 ARRAY = 0x3c02a4f0 FILL = 1 MAX = 3 ARYLEN = 0x0 FLAGS = (REAL) Elt No. 0 SV = NULL(0x0) at 0x3c006168 REFCNT = 1 FLAGS = () Elt No. 1 SV = NULL(0x0) at 0x3c006264 REFCNT = 1 FLAGS = () SV = RV(0x3c02b018) at 0x3c0062dc REFCNT = 1 FLAGS = (TEMP,ROK) RV = 0x3c011718 SV = PVAV(0x3c0084dc) at 0x3c011718 REFCNT = 2 FLAGS = () IV = 0 NV = 0 ARRAY = 0x3c02a4f0 FILL = 1 MAX = 3 ARYLEN = 0x0 FLAGS = (REAL) Elt No. 0 SV = UNKNOWN(0xff) (0x0) at 0x3c006168 REFCNT = 1 FLAGS = () Elt No. 1 SV = UNKNOWN(0xff) (0x0) at 0x3c006264 REFCNT = 1 FLAGS = ()
Note that the array entries changed from :
SV = NULL(0x0) at 0x3c006168
To:
SV = UNKNOWN(0xff) (0x0) at 0x3c006168

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[ambrus]: Corion: ah, so you want a library that parses HTTP, and you want to do the IO yourself, and don't want a full AnyEvent wrapper.
[ambrus]: Corion: I think I parsed a HTTP header from a string with LWP once. You can definitely use that to create a HTTP message too. The problme is
[ambrus]: that if you do that, you'd have to find where each HTTP response ends, which is nontrivial if you want persistent connections (essential for performance if you have small requests).
[Corion]: ambrus: Yes, ideally an API that I feed the incoming data piece by piece and that I can ask "is that response done" and "what should I do next" and "please construct the appropriate redirect for me"
[Corion]: ambrus: Yes, ideally the module would do all that nasty stuff for me and give me a way to ask it what the current situation is
[ambrus]: Corion: you could also consider using some wrapper over the multi interface of curl, I think Net::Curl might be a good one, since implementing enough of what it expects from the event loop might be easier than a full AnyEvent interface.
[ambrus]: Corion: you could also consider using IO::Async and its POE driver and some HTTP module for it, but I don't know if that would solve your problems with AnyEvent+POE
[ambrus]: Corion: wait, you didn't say POE. You said Prima, let me look up what that is.
[ambrus]: Corion: have you considered just writing an AnyEvent integration for that thing?
[ambrus]: Or perhaps pushing schmorp to write one?

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