Why doesn't reverse () change my array?

Question

When I use reverse() or sort() , I always need to store the return statement in a variable if I want to use it later.

 @array=qw(Nick Susan Chet Dolly Bill); @array = reverse(@array); 

Why is this different from using push() , pop() or shift() where you can just call a function and the array will be changed?

 @array=qw(Nick Susan Chet Dolly Bill); push(@array, "Bruce"); 

So what is the difference between these "functions"?

Answer 1

perldoc perlfunc provides a basic hint:

Functions for Real @ARRAYs

each , keys , pop , push , shift , splice , unshift , values

Functions for List Data

grep , join , map , qw// , reverse , sort , unpack

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And perldoc perlfaq4 explains the difference between arrays and lists (highlighting my own):

What is the difference between a list and an array?

(contributed by brian d foy)

A list is a fixed set of scalars. An array is a variable that contains a variable set of scalars. An array can provide collection for list operations, so list operations also work with arrays.

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Array operations that modify scalars, rearrange them, or add or subtract some scalars only work with arrays . They cannot work on a list that is fixed. Array operations include shift , unshift , push , pop and splice .

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In short, list operations, such as reverse , are for lists that cannot be changed.

The fact that they can accept arrays is just a side effect of list maintenance.

Answer 2

Just use:

 @array = reverse(@array) 

I probably would not recommend this, but if you really wanted you to be able to fix it ...:

 use Data::Dumper; use strict; use warnings; use subs 'reverse'; my @array=qw(Nick Susan Chet Dolly Bill); sub reverse(\@) { my $a = shift; @{$a} = CORE::reverse(@{$a}) } reverse(@array); print Dumper \@array; #$VAR1 = ['Bill','Dolly','Chet','Susan','Nick'];