Re: from array to hash

%b = map { $_ => 1 }
     grep defined, @a;
[download]

%b = map { defined ? ($_ => 1) : () } @a;
[download]

or you could avoid getting undef in the first place by using splice instead of delete or undef to delete the element from the array:

@a = qw( a b c d );

# Delete 1 starting at index 2.
# What used to be at index 3 is now at index 2.
splice(@a, 2, 1);

print("\@a has ", scalar(@a), "elements.\n");
[download]

Comment on Re: from array to hash Select or Download Code

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Re^2: from array to hash by jeanluca (Deacon) on Mar 09, 2006 at 15:44 UTC
Thanks, but what if the hash already has some values, like: `#! /usr/bin/perl @a = qw(a b c d ); $b{x} = 10 ; %b = map { $_, 1} splice(@a, 0, scalar(@a) ); print "$_ --> $b{$_}\n" foreach (keys %b) ;` [download] all values of %b are erased using map..... Furthermore, is scalar(@a) really necessary, or can you as well do @a ? Luca	[reply] [d/l]
Re^3: from array to hash by friedo (Prior) on Mar 09, 2006 at 15:48 UTC
In that case, you can use a loop instead: `$b{$_} = 1 for grep defined, @a;` [download]	[reply] [d/l]
Re^3: from array to hash by ikegami (Patriarch) on Mar 09, 2006 at 17:20 UTC
You've severly misunderstood the use of `splice`. Did you read the docs? `@a = qw(a b c d ); undef $a[2]; $b{x} = 10 ; $b{$_} = 1 foreach grep defined, @a;` [download] or `@a = qw(a b c d ); splice(@a, 2, 1); $b{x} = 10 ; $b{$_} = 1 foreach @a;` [download]	[reply] [d/l] [select]