將值從一個散列值複製到另一個散列值

Question

我有兩個哈希值，一大一小。所有較小的散列鍵都顯示在較大的散列表中，但值不同。我想從較大的散列值複製到較小的散列值。

EG：

# I have two hashes like so 
%big_hash = (A => '1', B => '2', C => '3', D => '4', E => '5'); 
%small_hash = (A => '0', B => '0', C => '0'); 
# I want small_hash to get the values of big_hash like this 
%small_hash = (A => '1', B => '2', C => '3'); 

一個明顯的答案是通過小散的鑰匙環，並複製值，這樣

foreach $key (keys %small_hash) { $small_hash{$key} = $big_hash{$key}; } 

有一個較短的方式做到這一點？

Answer 1

@small_hash{ keys %small_hash } = @big_hash{ keys %small_hash }; 

Answer 2

use strict; 
my %source = (a => 1, b => 2, c => 3); 
my %target = (a => -1, x => 7, y => 9); 

# Use a hash slice for the copy operation. 
# Note this will clobber existing values. 
# Which is probably what you intend here. 
@target{ keys %source } = values %source; 

for (sort keys %target) { 
    print $_, "\t", $target{ $_ }, "\n"; 
} 

Answer 3

這裏有一個方法，你可以做到這一點：

%small = map { $_, $big{$_} } keys %small; 

本書雖然那是相當相似的循環。

$small{$_} = $big{$_} for keys %small; 

---

mapproof爲那些需要一個：

my %big = (A => '1', B => '2', C => '3', D => '4', E => '5'); 
my %small = (A => '0', B => '0', C => '0'); 

%small = map { $_, $big{$_} } keys %small; 

print join ', ', %small; 

輸出：

A, 1, C, 3, B, 2