Beefy Boxes and Bandwidth Generously Provided by pair Networks
go ahead... be a heretic
 
PerlMonks  

Re: Re: undef'ing @arrays caveat

by dmmiller2k (Chaplain)
on Apr 20, 2002 at 22:46 UTC ( #160816=note: print w/replies, xml ) Need Help??


in reply to Re: undef'ing @arrays caveat
in thread undef'ing @arrays caveat

Actually, arrays cannot be undefined, just made empty (same with hashes). If you try undef @array in the debugger and then dump its value using the 'x' command, the effect is the same as if you had said @array = (), namely 'empty array'. (The same may be said for hashes, which under the above circumstances, produce the message, 'empty hash').

Only scalars may be truly undefined; undef is itself merely a value, albeit a special one. As a C/C++ programmer, I rather think of scalars analagous to pointers -- sort of "auto-allocating, auto-dereferencing, type-ambivalent pointers", but pointers nonetheless, with undef rather analagous to NULL.

dmm

If you GIVE a man a fish you feed him for a day
But,
TEACH him to fish and you feed him for a lifetime

Replies are listed 'Best First'.
Re: Re: Re: undef'ing @arrays caveat
by Kanji (Parson) on Apr 21, 2002 at 01:16 UTC

    I was thinking of definedness in the defined sense, but after some testing I discovered something really bizarre:

    Calling defined on an array that was declared as empty versus one that had been populated and then later emptied returns different results!

Log In?
Username:
Password:

What's my password?
Create A New User
Node Status?
node history
Node Type: note [id://160816]
help
Chatterbox?
and all is quiet...

How do I use this? | Other CB clients
Other Users?
Others surveying the Monastery: (10)
As of 2017-12-13 17:13 GMT
Sections?
Information?
Find Nodes?
Leftovers?
    Voting Booth?
    What programming language do you hate the most?




















    Results (371 votes). Check out past polls.

    Notices?