Re^2: merge two hashes into one

map could also be used to generate the sums of the intersection set of the two hashes (with no exceptions thrown):

c:\@Work\Perl\monks>perl -wMstrict -MData::Dump -le
"my %h1 = qw(a 1  b 2  c 3     );
 my %h2 = qw(     b 7  c 8  d 4);
 ;;
 my %h_out =
   map  exists $h2{$_} ? ($_ => $h1{$_} + $h2{$_}) : (),
   keys %h1
   ;
 dd \%h_out;
"
{ b => 9, c => 11 }
[download]

The exists test could be moved into a separate grep step for perhaps greater clarity, but I'd expect a bit of a performance hit with large hashes.

BTW: Won't
my %h3 = map {$_ => $h1{$_} + $h2{$_}} keys %h1, keys %h2;
cause "Use of uninitialized value ..." warnings unless that warning is disabled?

Give a man a fish: <%-{-{-{-<

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Re^3: merge two hashes into one by Tux (Canon) on May 30, 2018 at 11:24 UTC
`my %h1 = qw( a 1 b 2 c 3 ); my %h2 = qw( b 7 c 8 d 4 ); my %h3 = map { $_ => $h1{$_} // 0 + $h2{$_} // 0 } keys %h1, keys %h2;` [download] No warnings, merges both hashes Enjoy, Have FUN! H.Merijn	[reply] [d/l]
Re^4: merge two hashes into one by AnomalousMonk (Archbishop) on May 30, 2018 at 13:59 UTC
The expression `$h1{$_} // 0 + $h2{$_} // 0` has a complicated precedence: `c:\@Work\Perl\monks>perl -wMstrict -MO=Deparse,-p -le "my %h1 = qw( a 1 b 2 c 3 ); my %h2 = qw( b 7 c 8 d 4 ); my %h3 = map { $_ => $h1{$_} // 0 + $h2{$_} // 0 } keys %h1, keys %h2 +; " BEGIN { $^W = 1; } BEGIN { $/ = "\n"; $\ = "\n"; } use strict 'refs'; (my(%h1) = ('a', '1', 'b', '2', 'c', '3')); (my(%h2) = ('b', '7', 'c', '8', 'd', '4')); (my(%h3) = map({($_, (($h1{$_} // (0 + $h2{$_})) // 0));} keys(%h1), k +eys(%h2))); -e syntax OK` [download] Are you sure it works in all circumstances? Wouldn't it be better to throw in a couple pair disambiguating parentheses? E.g.: `($h1{$_} // 0) + ($h2{$_} // 0)` Give a man a fish: `<%-{-{-{-<`	[reply] [d/l] [select]