array initialization

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

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Re: array initialization by Dominus (Parson) on Nov 13, 2000 at 09:11 UTC
To fill an array with zeroes, use: `@a = (0) x 143; # 143 zeroes` [download] Or if the array already has the length you want, and you want to make every element zero, use: `@a = (0) x @a; # every element set to zero` [download] But often, the best thing to do is just destroy what's in the array: `undef @a;` [download] If you undefine the array, and then try to look at the elements, they will be undefined, and an undefined array element behaves like 0 if you use it as a number. For example: `undef @a; $z = $a[3] + 12; print $z;` [download] This prints 12.	[reply] [d/l] [select]
Re: array initialization by merlyn (Sage) on Nov 13, 2000 at 18:02 UTC
`@a = (0) x @a; # every element set to zero` [download] An alternative to that which is probably faster for large arrays is: `$_ = 0 for @a;` [download] -- Randal L. Schwartz, Perl hacker	[reply] [d/l] [select]
(tye)Re: array initialization by tye (Sage) on Nov 14, 2000 at 01:35 UTC
Note I tend to "clear" an array using: `@a= ();` [download] and not with: `undef @a;` [download] The difference is that `undef @a` will free the memory allocated for the array. If you have put a really huge number of elements into @a and don't plan on doing that again for quite a while, then you probably do want to use `undef @a` to allow that memory to be reused in the mean time. Otherwise, `@a= ()` is probably a better choice as it removes the overhead of freeing and then later reallocating memory. Also note that `@a= ()` does free the memory allocated for the elements of the array (except for elements that have other references to them). - tye (but my friends call me "Tye")	[reply] [d/l] [select]