Re^3: Newbies question: initializing data structure

specifically, I noticed my @arr = {map { }, 1 .. $arr_len} seems to work, rather than my first guess, which was my @arr = [map { }, 1 .. $arr_len].

But shouldn't we return a array to assign into @arr? hence use square brackets?

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Re^4: Newbies question: initializing data structure by almut (Canon) on Jun 02, 2010 at 11:18 UTC
`[ ]` and `{ }` return an array and a hash reference respectively, i.e. a scalar. That scalar is assigned to the first element of `@arr`. If you want to fill the array with the elements created by `map`, you probably just want `my @arr = map { }, 1 .. $arr_len;` [download] or maybe `my $arrayref = [ map { }, 1 .. $arr_len ];` [download] As to the former variant, you can also put parentheses around the list (to make it clear it is a list) `my @arr = ( map { }, 1 .. $arr_len );` [download] but syntactically they're not required in this case. P.S.: with `{map { }, 1..$arr_len}` you'd run into problems with an odd-number `$arr_len`, because hashes need to be initialized from key/value pairs... But using anonymous hashes (`{}`) as hash keys only is of limited use anyway (they'd end up stringified like `'HASH(0x63aa80)'`) — and probably not what you meant.	[reply] [d/l] [select]

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Re^4: Newbies question: initializing data structure
by almut (Canon) on Jun 02, 2010 at 11:18 UTC

[ ] and { } return an array and a hash reference respectively, i.e. a scalar. That scalar is assigned to the first element of @arr. If you want to fill the array with the elements created by map, you probably just want

my @arr = map { }, 1 .. $arr_len;
[download]

or maybe

my $arrayref = [ map { }, 1 .. $arr_len ];
[download]

As to the former variant, you can also put parentheses around the list (to make it clear it is a list)

my @arr = ( map { }, 1 .. $arr_len );
[download]

but syntactically they're not required in this case.

P.S.: with {map { }, 1..$arr_len} you'd run into problems with an odd-number $arr_len, because hashes need to be initialized from key/value pairs... But using anonymous hashes ({}) as hash keys only is of limited use anyway (they'd end up stringified like 'HASH(0x63aa80)') — and probably not what you meant.

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