In Perl is it possible to transform an array using another array position by position?

Question

I have an array of values which I'd like to transform using another array, like so

@raw_values      = qw(10 20 30 40);

@adjustment_factors = qw(1 2 3 4);


#the expected value array
@expected_values    = qw(10 40 90 160);

Is there a more perlish way to doing that then this?

for my $n (0..$#raw_values){
    $expected_values[ $n ] = $raw_values[ $n ] * $adjustment_factors[ $n ]
}

The arrays always have the same number of elements, and I have a few thousand to process.

choroba · Accepted Answer · 2013-02-08 12:32:55Z

4

Use map:

@expected_values = map { $raw_values[$_] * $adjustment_factors[$_] } 0 .. $#raw_values;

Another option is to first assign the original values and then modify them:

@expected_values = @raw_values;
$x = 0;
$_ *= $adjustment_factors[$x++] for @expected_values;

Or, if you do not need @adjustment_factors anymore, you can empty it:

@expected_values = map { $_ * shift @adjustment_factors } @raw_values;

edited Feb 8, 2013 at 12:32

answered Feb 8, 2013 at 12:25

choroba

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kaklon Over a year ago

Excellent, just what I was looking for

Axeman · Accepted Answer · 2013-02-08 13:24:34Z

3

pairwise is the more idiomatic, CPAN solution.

use List::MoreUtils qw<pairwise>;

my @expected_values = pairwise { $a * $b } @raw_values, @adjustment_factors;

See List::MoreUtils

answered Feb 8, 2013 at 13:24

Axeman

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Axeman Over a year ago

@choroba,the outstanding "bugs" tend to follow a couple patterns. The biggest one is "Wishlist"--it's somebody's idea of something they would like MoreUtils to do, but it doesn't. The next group are things that are not officially marked as fix, but if you take a look at the thread, a fix was put in. And then, there are issues like if you pass the XS version a "bad array reference", you get a segfault. So, the trick is not to pass it a bad array reference. I worked at a Perl shop where a lot of guys used this mod pretty heavily.

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