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### Re: diff of two hashes.

by Russ (Deacon)
 on May 12, 2000 at 20:59 UTC ( #11320=note: print w/replies, xml ) Need Help??

in reply to diff of two hashes.

<Updated>
I like nuance's idea (above). I now store undef as the value when a key is missing from one hash. See nuance's description above for an explanation of the "return" values.
</Updated>

Here's some punctuation for you:

(This is a short, concentrated way to do it - only 4 lines)

```# Keys 7 and 8 are unique, keys 2,4 and 6 have different values
my %R = (1=>1, 2=>2,   3=>3, 4=>4,   5=>5, 6=>6,   7=>7);
my %S = (1=>1, 2=>'b', 3=>3, 4=>'d', 5=>5, 6=>'f', 8=>8);

# 1) Keys in %R which are not in %S
# 2) Keys in %S which are not in %R
# 3) Keys in both which have different values
my %Diffs = ((map((\$_ => [\$R{\$_}, undef]),  grep {not exists \$S{\$_}} k
+eys %R)),
(map((\$_ => [undef,  \$S{\$_}]), grep {not exists \$R{\$_}} k
+eys %S)),
(map((\$_ => [\$R{\$_}, \$S{\$_}]),
grep {exists \$S{\$_} and \$R{\$_} ne \$S{\$_}}  keys %R))
+);

# Print out what we found
for (sort keys %Diffs){
print \$_, ': ', join(', ', map(defined \$_ ? \$_ : 'undef', @{\$Diffs{\$
+_}})), "\n";
}
A couple points to note:
• if your values are numeric, change the 'ne' in the third Diffs section
• we use an anonymous array ref to store the values in %Diffs, so remember to dereference it when you use %Diffs

Enjoy!

Russ

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