| PerlFAQ Server 2004-11-26, 4:02 am |
| This message is one of several periodic postings to comp.lang.perl.misc
intended to make it easier for perl programmers to find answers to
common questions. The core of this message represents an excerpt
from the documentation provided with Perl.
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4.49: How do I process/modify each element of an array?
Use "for"/"foreach":
for (@lines) {
s/foo/bar/; # change that word
y/XZ/ZX/; # swap those letters
}
Here's another; let's compute spherical volumes:
for (@volumes = @radii) { # @volumes has changed parts
$_ **= 3;
$_ *= (4/3) * 3.14159; # this will be constant folded
}
which can also be done with map() which is made to transform one list
into another:
@volumes = map {$_ ** 3 * (4/3) * 3.14159} @radii;
If you want to do the same thing to modify the values of the hash, you
can use the "values" function. As of Perl 5.6 the values are not copied,
so if you modify $orbit (in this case), you modify the value.
for $orbit ( values %orbits ) {
($orbit **= 3) *= (4/3) * 3.14159;
}
Prior to perl 5.6 "values" returned copies of the values, so older perl
code often contains constructions such as @orbits{keys %orbits} instead
of "values %orbits" where the hash is to be modified.
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