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### Cost of list assignment -

by mimiandi (Novice)
 on Jan 31, 2013 at 09:17 UTC Need Help??
mimiandi has asked for the wisdom of the Perl Monks concerning the following question:

Hi just wondering what the cost of doing list assignment as below in perl? Very useful, but wondering if this costs more than than doing it otherways

(\$num, \$num2) = (\$num3, \$num4);

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Re: Cost of list assignment -
by BrowserUk (Pope) on Jan 31, 2013 at 09:38 UTC
but wondering if this costs more than than doing it otherways

Yes, measurably so:

```@a=1..1e6;
cmpthese -3,{
a => q[ @a[ \$_-1, \$_ ] = @a[ \$_, \$_-1 ] for 1 .. \$#a; ],
b => q[ my\$t; \$t = \$a[ \$_-1 ], \$a[ \$_-1 ] = \$a[ \$_ ], \$a[ \$_ ] = \$
+t for 1 .. \$#a; ]
};;
Rate   a   b
a 1.58/s  -- -5%
b 1.66/s  5%  --

but the difference is tiny, so only becomes significant in inner loops with high iteration factors.

Other times the clarity is worth the cost.

With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday'
Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
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Re: Cost of list assignment -
by choroba (Bishop) on Jan 31, 2013 at 09:34 UTC
If you are getting paid for the number of lines, it costs you one line.

The real power of list assignment is

```(\$x, \$y) = (\$y, \$x);
No temporary variable!
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