> $hash{(split)[0]}{(split)[1]} = 1 foreach <>;

> How can I achieve a similar result using map?

not "really", to do so you would need to use map in void context in order to act like foreach!

  DB<163> map { ($a,$b)=split /\s+/; $hash{$a}{$b}=1 } <I>;
 => (1, 1, 1, 1)

  DB<164> \%hash
 => { Canberra => { 12 => 1, 18 => 1 }, Sydney => { 12 => 1, 14 => 1 }
+ }

[download]

(Please note that you are calling split twice, I avoided this by setting $a and $b and have full control over the delimiter.)

You can't have map returning nested hashes assigned to a top-level hash, otherwise entries from different lines would collide (2 x Sidney, 2 x Canberra) and be overwritten:

 %hash = map { entry1 => { entry2 => 1} } <> # collisions of entry1

Another concise way to do it, involving a "real" map and avoiding named variables:

  DB<143> $hash{$_->[0]}{$_->[1]} = 1 for map { [split /\s+/] } <I>
 => ""

  DB<144> \%hash
 => { Canberra => { 12 => 1, 18 => 1 }, Sydney => { 12 => 1, 14 => 1 }
+ }

[download]

Of course creating an anonymous array is not optimal...

Cheers Rolf

( addicted to the Perl Programming Language)

In reply to Re: Possible for Map to create Hash of Hash? by LanX
in thread Possible for Map to create Hash of Hash? by konnjuta

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