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perl hash - using a range as a hash key.


 
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# 1  
Old 08-31-2010
perl hash - using a range as a hash key.

Hi,

In Perl, is it possible to use a range of numbers with '..' as a key in a hash?

Something in like:

Code:
%hash = (
                 '768..1536' => '1G',
                 '1537..2560' => '2G'
                );

That is, the range operation is evaluated, and all members of the range are 'mapped' to the RHS value, so that for the first keypair, '1000' would return 1G.

I think somehow 'map' might be what i'm after, but can't find any reference material to support my theory.

Any advice welcome,

cheers

dsw

Last edited by dsw; 08-31-2010 at 06:46 AM.. Reason: typo
# 2  
Old 08-31-2010
One way to construct this:
Code:
%hash = map { $a = '1G' if /768/ .. /1536/; $a = '2G' if /1537/ .. /2560/; $_ => $a }
  768 .. 2560;

These 2 Users Gave Thanks to pludi For This Post:
# 3  
Old 08-31-2010
Could I suggest a different approach?
Code:
perl -le'
  
  $val = shift;
  
  @ranges = (
     [768, 1536, "1G"],
     [1537, 2560, "2G"]
     ); 
     
  for (@ranges) {
    print $_->[2] and last 
      if $_->[0] <= $val && $val <= $_->[1]
    }
  '

It produces:

Code:
% perl -le'

  $val = shift;

  @ranges = (
     [768, 1536, "1G"],
 [1537, 2560, "2G"]
 );

  for (@ranges) {
    print $_->[2] and last
      if $_->[0] <= $val && $val <= $_->[1]
    }
  ' 1000
1G
% perl -le'

  $val = shift;

  @ranges = (
     [768, 1536, "1G"],
 [1537, 2560, "2G"]
 );

  for (@ranges) {
    print $_->[2] and last
      if $_->[0] <= $val && $val <= $_->[1]
    }
  ' 2000
2G

This User Gave Thanks to radoulov For This Post:
# 4  
Old 08-31-2010
Awesome, thank you both pludi and radoulov - both very workable solutions.

cheers

dsw.

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