Better way to do array addition in Perl?

Question

Code

use List::MoreUtils 'pairwise'; # http://stackoverflow.com/a/1865966/54964
my @offset = (0.28)x scalar(@x); # http://www.perlmonks.org/?node_id=110603
my @x = pairwise { $a + $b } @x, @offset;

I would like find a better way to this by default tools.

Is there any better way to do array addition in Perl?

score 6 · Accepted Answer · answered Apr 03 '15 at 10:05

6

There is no need for a pairwise array summation here: That is an issue created your choice to create a second array as big as the original one (at least doubling the memory footprint of your program).

All you are doing is to add a constant to every element of @x. Use a for loop:

$_ += 0.28 for @x;

answered Apr 03 '15 at 10:05

Sinan Ünür

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Excellent answer! I like to keep the memory footprint constant. – Léo Léopold Hertz 준영 Apr 03 '15 at 10:15
What is the difference between this command and your command in the comment with the map? I think both have the same memory footprint, just different implementation of two commands. Actually, the command in the comment does not seem to work in my system. – Léo Léopold Hertz 준영 Apr 03 '15 at 10:17
This command *@x = map $_ += 0.28, @x;* produces the same as the command in your answer. Without *@x = ...*, no storage. My Perl is 5.18.2 so new one. – Léo Léopold Hertz 준영 Apr 03 '15 at 10:51

score 2 · Answer 2 · answered Apr 03 '15 at 12:49

2

First make it work, then make it better. Or in other words, avoid premature optimization.

my $offset = 0.28;
for my $x_value ( @x ){
    $x_value += $offset;
}

Simple means those who have to maintain your code will like you. ☻

answered Apr 03 '15 at 12:49

shawnhcorey

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Better way to do array addition in Perl?

2 Answers2