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Kevin Ryde > Perl-Critic-Pulp > Perl::Critic::Policy::ValuesAndExpressions::ProhibitArrayAssignAref



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Perl::Critic::Policy::ValuesAndExpressions::ProhibitArrayAssignAref - don't assign an anonymous arrayref to an array


This policy is part of the Perl::Critic::Pulp add-on. It asks you not to assign an anonymous arrayref to an array

    @array = [ 1, 2, 3 ];       # bad

The idea is that it's rather unclear whether an arrayref is intended, or might have meant to be a list like

    @array = ( 1, 2, 3 );

This policy is under the "bugs" theme (see "POLICY THEMES" in Perl::Critic) for the chance [] is a mistake, and since even if it's correct it will likely make anyone reading it wonder.

A single arrayref can still be assigned to an array, but with parens to make it clear,

    @array = ( [1,2,3] );       # ok

Dereferences or array and hash slices (see "Slices" in perldata) are recognised as an array target and treated similarly,

    @$ref = [1,2,3];            # bad assign to deref
    @{$ref} = [1,2,3];          # bad assign to deref
    @x[1,2,3] = ['a','b','c'];  # bad assign to array slice
    @x{'a','b'} = [1,2];        # bad assign to hash slice

List Assignment Parens

This policy is not a blanket requirement for () parens on array assignments. It's normal and unambiguous to have a function call or grep etc without parens.

    @array = foo();                    # ok
    @array = grep {/\.txt$/} @array;   # ok

The only likely problem from lack of parens in such cases is that the , comma operator has lower precedence than = (see perlop), so something like

    @array = 1,2,3;   # oops, not a list


    @array = (1);

Normally the remaining literals in void context provoke a warning from Perl itself.

An intentional single element assignment is quite common as a statement, for instance

    @ISA = 'My::Parent::Class';   # ok

And for reference the range operator precedence is high enough,

    @array = 1..10;               # ok

But of course parens are needed if concatenating some disjoint ranges with the comma operator,

    @array = (1..5, 10..15);      # parens needed

The qw form gives a list too

    @array = qw(a b c);           # ok


Perl::Critic, Perl::Critic::Pulp



Copyright 2011, 2012, 2013, 2014, 2015, 2016, 2017 Kevin Ryde

Perl-Critic-Pulp is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 3, or (at your option) any later version.

Perl-Critic-Pulp is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with Perl-Critic-Pulp. If not, see <>.

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