in reply to small steps toward Perl literacy, temp vars and parentheses

I'd code that as 

use List::Util qw[ min ];

%h = map{ 
    $_, $h{ $_ } 
} min keys %h;

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Which I think clarifies things a lot as well as saving a little runtime.

I also favour breaking chains over several lines as I think it makes it easier to pick out what is going on.

If I needed to keep the lowest 2 or more elements then 

%h = map{ 
    $_, $h{ $_ } 
} ( sort{ $a <=> $b } keys %h )[ 0 .. 2 ];

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Examine what is said, not who speaks.
"Efficiency is intelligent laziness." -David Dunham
"Think for yourself!" - Abigail
"Memory, processor, disk in that order on the hardware side. Algorithm, algoritm, algorithm on the code side." - tachyon

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Re^2: small steps toward Perl literacy, temp vars and parentheses
by BlaisePascal (Monk) on Jun 17, 2004 at 00:03 UTC
    Hmm, your solution for keeping the lowest 2 or more elements still puts the indexing at the end, but it changes the op structure to  %h = op4 (op2 op1 %h) op3 which from a jumping back and forth from beginning to end issue is worse. But it does change the structure in another way that suggests: 
    %h = map { $_, $h{ $_ } }
         shift sort { $a <==> $b } keys %h;

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    (that, by the way, is completely untested. Hmm, testing says it doesn't work, type of arg 1 of shift must be array, not sort. i wasn't aware that sort was a type. I wonder how to do what I want...)
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      I guess we read the code in different ways. I don't think of the code as a list of operations applied to %h, but as assigning the results of map to %h.

      map takes a list and manipulates it. The fact that the input to map is also derived from %h is effectively moot. It could equally well be a completely different hash.

      I look at 

      %h = map{
    $_, $h{ $_ }
} ( sort{ $a <=> $b } keys %h )[ 0 .. 2 ];

      [download]

      as: Take the first 3 from a list of sorted keys and feed them to map. Map those keys to key/value pairs and assign them to %h.

      Examine what is said, not who speaks.
      "Efficiency is intelligent laziness." -David Dunham
      "Think for yourself!" - Abigail
      "Memory, processor, disk in that order on the hardware side. Algorithm, algoritm, algorithm on the code side." - tachyon
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In Section Meditations