in reply to Comparing two text files and marking differences

Here's your examples run through a word diff'r by color I had laying around. Maybe this could be a starting point for solving your problem. 

#!/usr/bin/perl

use strict; # https://perlmonks.org/?node_id=11127688
use warnings;
use Algorithm::Diff qw(traverse_sequences);
use Term::ANSIColor;

while( <DATA> )
  {
  my @from = split /(\s+)/;
  my @to = split /(\s+)/, <DATA>;

  traverse_sequences( \@from, \@to,
    {
    MATCH     => sub {print $from[shift()]},
    DISCARD_A => sub {print color('red'), $from[shift()], color 'reset
+'},
    DISCARD_B => sub {print color('green'), $to[pop()], color 'reset'}
+,
    } );
  print "\n\n";
  }

__DATA__
A few moments will suffice to commit it to memory; yet the period whic
+h it covers, commencing more than twenty-five centuries ago, reaches 
+on from that far-distant point past the rise and fall of kingdoms, pa
+st the setting up and overthrow of empires, past cycles and ages, pas
+t our own day, over into the eternal state.
A few moments will suffice to commit it to memory, yet the period whic
+h it covers, beginning more than twenty-five centuries ago, reaches f
+rom that far-distant point past the rise and fall of kingdoms, past t
+he setting up and overthrow of empires, past cycles and ages, past ou
+r own day, to the eternal state.
Now opens one of the sublimest chapters of human history.
Now opens one of the most comprehensive of the histories of world empi
+res.
With what interest, as well as astonishment, must the king have listen
+ed, as he was informed by the prophet that he, or rather his kingdom,
+ the king being here put for his kingdom (see the following verse), w
+as the golden head of the magnificent image which he had seen.
With what interest and astonishment must the king have listened as he 
+was informed by the prophet that his kingdom was the golden head of t
+he magnificent image.

[download]

Replies are listed 'Best First'.
Re^2: Comparing two text files and marking differences
by Polyglot (Chaplain) on Jan 31, 2021 at 07:20 UTC

    I appreciate all of the answers, and found that I was able to make some modifications to this one in particular which seems to be yielding most of what I want. I'm still doing a few post-subroutine substitutions to clear up some text formatting issues, but the following subroutine does the bulk of what needed to be done.

    sub comparator {
my $str1 = shift @_;
my $str2 = shift @_;
my $original = '';
my $revised  = '';

my @from = split(/((?:<[^>]+>)+|(?:\s)+|(?:\w[A-Za-z'-]*\w*)+|(?:\W|\P
+{IsWord})|(?:\p{IsDigit}))/, $str1);
my @to   = split(/((?:<[^>]+>)+|(?:\s)+|(?:\w[A-Za-z'-]*\w*)+|(?:\W|\P
+{IsWord})|(?:\p{IsDigit}))/, $str2);

my $OS = qq|<span class="m">|;
my $OE = qq|</span> |;
my $RS = qq|<span class="hl">|;
my $RE = qq|</span> |;

  traverse_sequences( \@from, \@to,
    {
    MATCH     => sub { my $oldtext = $from[shift()]; $original .= $old
+text; $revised .= $oldtext },
    DISCARD_A => sub { my $oldtext = $from[shift()]; if ($oldtext =~ m
+/(?:\p{IsPunct})|(?:\s)/) {$original .= $oldtext } else { $original .
+= $OS.$oldtext.$OE } },
    DISCARD_B => sub { my $newtext = $to[pop()];     if ($newtext =~ m
+/(?:\p{IsPunct})|(?:\s)/) {$revised  .= $newtext } else { $revised  .
+= $RS.$newtext.$RE } },
    } );
    
    return ($original, $revised);
    
} #END SUB comparator

    [download]

    I have never found the output of a standard diff to be very enlightening. I'm sure it works well to change files, patch-style, but it isn't very readable for someone simply wanting to see what happened to the text in a side-by-side format. This procedure is making a visual inspection much easier, with the help of some HTML markup.

    Thank you!

    Blessings,

    ~Polyglot~

[reply]
[d/l]
      I have never found the output of a standard diff to be very enlightening. I'm sure it works well to change files, patch-style, but it isn't very readable for someone simply wanting to see what happened to the text in a side-by-side format.

      Plain old diff (in the GNU version) has at least four output formats:

      • ed script: 
        /tmp>diff foo bar
1,2c1,2
< Bla bla. Foo bar baz.
< Nada nada nada. Nada?
---
> Bla bar. Foo bar baz.
> Nada na-da nada. Nada?
4c4
< bar. Bla. Bar bla.
---
> bar. Bla bar bla.

        [download]
      • Unified: 
        /tmp>diff -u foo bar
--- foo 2021-01-31 15:13:16.892239748 +0100
+++ bar 2021-01-31 15:13:43.403869518 +0100
@@ -1,6 +1,6 @@
-Bla bla. Foo bar baz.
-Nada nada nada. Nada?
+Bla bar. Foo bar baz.
+Nada na-da nada. Nada?
 Foo foo foo! Bar. Foo
-bar. Bla. Bar bla.
+bar. Bla bar bla.
 Foo bla bla nada bar.

        [download]
      • Side by side (also available via sdiff) 
        /tmp>diff -y foo bar
Bla bla. Foo bar baz.                                         | Bla ba
+r. Foo bar baz.
Nada nada nada. Nada?                                         | Nada n
+a-da nada. Nada?
Foo foo foo! Bar. Foo                                           Foo fo
+o foo! Bar. Foo
bar. Bla. Bar bla.                                            | bar. B
+la bar bla.
Foo bla bla nada bar.                                           Foo bl
+a bla nada bar.

        [download]
      • rcs 
        /tmp>diff -n foo bar
d1 2
a2 2
Bla bar. Foo bar baz.
Nada na-da nada. Nada?
d4 1
a4 1
bar. Bla bar bla.

        [download]

      TortoiseSVN comes with a diff and merge tool called TortoiseMerge that can show changes side by side, highlighting not only changed lines, but also changes within the lines.

      Side note:

      sub comparator {
my $str1 = shift @_;
#...
my $RE = qq|</span> |;

  traverse_sequences( \@from, \@to,
    {
    # ...
    } );
    
    return ($original, $revised);
    
} #END SUB comparator

      [download]

      Proper indenting would make the "#END SUB comparator" redundant:

      sub comparator 
{
    my $str1 = shift @_;
    #...
    my $RE = qq|</span> |;

    traverse_sequences( \@from, \@to,
        {
            # ...
        }
    );
    
    return ($original, $revised);
}

      [download]

      Alexander

      --
      Today I will gladly share my knowledge and experience, for there are no sweeter words than "I told you so". ;-)
[reply]
[d/l]
[select]

        Regarding the proper indenting making my comment "redundant":

        I use indenting as well, but I tend to have subroutines that extend well beyond one screen's worth of code. I like having that note at the bottom just to help guide me in locating my position within the file as I'm scanning. I've developed a habit for doing it this way, and it's not going to change!

        Remember, TMTOWTDI. This is my way.

        Blessings,

        ~Polyglot~

[reply]

In Section Seekers of Perl Wisdom