Comparing hash structures?

[ericse]

Hello all,

I'm trying to compare hash structures and return the unique values of each hash.

my $hash1 = { 'add' => { 'val1' => 1,
                         'val2' => 1,
                         'val3' => 1 },
             'remove' => { 'val4' => 0,
                           'val5' => 0,
                           'val6' => 0 }};
my $hash2 = { 'add' => { 'val1' => 1,
                         'val2' => 1,
                         'val3' => 1,
                         'val7' => 1},
             'remove' => { 'val4' => 0,
                           'val5' => 0,
                           'val6' => 0 }};

Now basically, when they're compared, I want a hash structure returned showing me that hash2 has 1 additional 'add' value (in this it being val7). Comparing the two's equality is relatively easy; finding the diff between one or the other is what I'm having trouble with.

I've read that I can use grep do to this, but from my limited experience using Perl's grep, I thought it only worked on arrays. Any help would be much appreciated.

 

[MillerH]

Just make a function to recursively search through your primary hash.

[url=http://perldoc.perl.org/functions/use.html][black][b]use[/b][/black][/url] [green]strict[/green][red];[/red]

[url=http://perldoc.perl.org/functions/my.html][black][b]my[/b][/black][/url] [blue]$hash1[/blue] = [red]{[/red]
	[red]'[/red][purple]add[/purple][red]'[/red] => [red]{[/red]
		[red]'[/red][purple]val1[/purple][red]'[/red] => [fuchsia]1[/fuchsia],
		[red]'[/red][purple]val2[/purple][red]'[/red] => [fuchsia]1[/fuchsia],
		[red]'[/red][purple]val3[/purple][red]'[/red] => [fuchsia]1[/fuchsia],
	[red]}[/red],
	[red]'[/red][purple]remove[/purple][red]'[/red] => [red]{[/red]
		[red]'[/red][purple]val4[/purple][red]'[/red] => [fuchsia]0[/fuchsia],
		[red]'[/red][purple]val5[/purple][red]'[/red] => [fuchsia]0[/fuchsia],
		[red]'[/red][purple]val6[/purple][red]'[/red] => [fuchsia]0[/fuchsia],
	[red]}[/red],
[red]}[/red][red];[/red]

[black][b]my[/b][/black] [blue]$hash2[/blue] = [red]{[/red]
	[red]'[/red][purple]add[/purple][red]'[/red] => [red]{[/red]
		[red]'[/red][purple]val1[/purple][red]'[/red] => [fuchsia]1[/fuchsia],
		[red]'[/red][purple]val2[/purple][red]'[/red] => [fuchsia]1[/fuchsia],
		[red]'[/red][purple]val3[/purple][red]'[/red] => [fuchsia]1[/fuchsia],
		[red]'[/red][purple]val7[/purple][red]'[/red] => [fuchsia]1[/fuchsia],
	[red]}[/red],
	[red]'[/red][purple]remove[/purple][red]'[/red] => [red]{[/red]
		[red]'[/red][purple]val4[/purple][red]'[/red] => [fuchsia]0[/fuchsia],
		[red]'[/red][purple]val5[/purple][red]'[/red] => [fuchsia]0[/fuchsia],
		[red]'[/red][purple]val6[/purple][red]'[/red] => [fuchsia]0[/fuchsia],
	[red]}[/red],
[red]}[/red][red];[/red]

[black][b]my[/b][/black] [blue]$diff[/blue] = [maroon]hash_diff[/maroon][red]([/red][blue]$hash2[/blue], [blue]$hash1[/blue][red])[/red][red];[/red]

[black][b]use[/b][/black] [green]Data::Dumper[/green][red];[/red]
[url=http://perldoc.perl.org/functions/print.html][black][b]print[/b][/black][/url] [maroon]Dumper[/maroon][red]([/red][blue]$diff[/blue][red])[/red][red];[/red]

[gray][i]# Hash Difference[/i][/gray]
[gray][i]# - Works on perfect matches only, with keys and values.[/i][/gray]
[gray][i]# - Implemented Recursively, but only with hash reference or string[/i][/gray]
[gray][i]#   values[/i][/gray]
[gray][i]# - Does not necessarily clone internal structures[/i][/gray]
[url=http://perldoc.perl.org/functions/sub.html][black][b]sub[/b][/black][/url] [maroon]hash_diff[/maroon] [red]{[/red]
	[gray][i]# Per [URL unfurl="true"]http://en.wikipedia.org/wiki/Subtraction[/URL][/i][/gray]
	[gray][i]# c - b = a  =>  are minuend (c) - subtrahend (b) = difference[/i][/gray]
	[black][b]my[/b][/black] [red]([/red][blue]$minuend[/blue], [blue]$subtrahend[/blue][red])[/red] = [blue]@_[/blue][red];[/red]
	
	[black][b]my[/b][/black] [blue]%diff[/blue][red];[/red]
	[olive][b]while[/b][/olive] [red]([/red][black][b]my[/b][/black] [red]([/red][blue]$key[/blue], [blue]$val[/blue][red])[/red] = [url=http://perldoc.perl.org/functions/each.html][black][b]each[/b][/black][/url] [blue]%$minuend[/blue][red])[/red] [red]{[/red]
		[gray][i]# Doesn't exist at all[/i][/gray]
		[olive][b]if[/b][/olive] [red]([/red][url=http://perldoc.perl.org/functions/exists.html][black][b]exists[/b][/black][/url] [blue]$subtrahend[/blue]->[red]{[/red][blue]$key[/blue][red]}[/red][red])[/red] [red]{[/red]
			[black][b]my[/b][/black] [blue]$subval[/blue] = [blue]$subtrahend[/blue]->[red]{[/red][blue]$key[/blue][red]}[/red][red];[/red]
			[gray][i]# Ref type comparison[/i][/gray]
			[olive][b]if[/b][/olive] [red]([/red][url=http://perldoc.perl.org/functions/ref.html][black][b]ref[/b][/black][/url][red]([/red][blue]$val[/blue][red])[/red] eq [black][b]ref[/b][/black][red]([/red][blue]$subval[/blue][red])[/red][red])[/red] [red]{[/red]
				[gray][i]# Comparison of each type[/i][/gray]
				[olive][b]if[/b][/olive] [red]([/red]! [black][b]ref[/b][/black] [blue]$val[/blue][red])[/red] [red]{[/red]
					[olive][b]next[/b][/olive] [olive][b]if[/b][/olive] [blue]$val[/blue] eq [blue]$subval[/blue][red];[/red]
					
				[red]}[/red] [olive][b]elsif[/b][/olive] [red]([/red][black][b]ref[/b][/black][red]([/red][blue]$val[/blue][red])[/red] eq [red]'[/red][purple]HASH[/purple][red]'[/red][red])[/red] [red]{[/red]
					[blue]$val[/blue] = [maroon]hash_diff[/maroon][red]([/red][blue]$val[/blue], [blue]$subval[/blue][red])[/red][red];[/red]
					[olive][b]next[/b][/olive] [olive][b]if[/b][/olive] ! [url=http://perldoc.perl.org/functions/keys.html][black][b]keys[/b][/black][/url] [blue]%$val[/blue][red];[/red]
					
				[red]}[/red] [olive][b]else[/b][/olive] [red]{[/red]
					[url=http://perldoc.perl.org/functions/die.html][black][b]die[/b][/black][/url] [red]"[/red][purple]Invalid ref type at [blue]$key[/blue][/purple][red]"[/red][red];[/red]
				[red]}[/red]
			[red]}[/red]
		[red]}[/red]

		[blue]$diff[/blue][red]{[/red][blue]$key[/blue][red]}[/red] = [blue]$val[/blue][red];[/red]
	[red]}[/red]
	
	[url=http://perldoc.perl.org/functions/return.html][black][b]return[/b][/black][/url] \[blue]%diff[/blue][red];[/red]
[red]}[/red]

[tt]------------------------------------------------------------
Pragmas (perl 5.8.8) used :
[ul]
[li]strict - Perl pragma to restrict unsafe constructs[/li]
[/ul]
Core (perl 5.8.8) Modules used :
[ul]
[li]Data:umper - stringified perl data structures, suitable for both printing and eval[/li]
[/ul]
[/tt]

- Miller