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The problem with text compare tools - similar, in database compare tools

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wraith808:
I haven't chimed in because... I'm not really getting the problem (and the general tone was why I didn't ask before).  Any decent diff program has to be able to know if a block has moved.  Right?

I took david.p's post above, saved it, then took a block of text and moved it.

This is the result:

The problem with text compare tools - similar, in database compare tools

Is there something obvious and/or simple that I'm missing?  Every diff tool that I know of can sense that sort of difference.

David.P:
Does anybody have an update on the ability of CompareIt! to detect moved words, lines, or blocks?
-Scott_Y (April 21, 2015, 11:07 AM)
--- End quote ---

It seems that CompareIt sort of detects entire moved paragraphs, but only if they are verbatim the same. As soon as you move a paragraph and make whatever little change to it, it is not detected as a move anymore. Also, CompareIt does not seem to detect smaller moved sections of text, only entire paragraphs.

Every diff tool that I know of can sense [moved text blocks].-wraith808 (April 21, 2015, 11:20 AM)
--- End quote ---

Of course, every diff tool will highlight moved text in some way as having been changed (like deleted/added). However, almost none of the known tools actually is able to show that moved text actually has been moved (and from where to where it has been moved). Instead, most tools show moved text as having been deleted at the original spot, and added at the target spot, without showing that this deletion/addition pair actually belongs together.

wraith808:
If you look at my screenshot, I've squished the map bar... but you see the red line connecting the two blocks of text?  That's exactly what that's saying.  And every diff tool that *I've* used does that.

Another example from Code Compare

The problem with text compare tools - similar, in database compare tools

David.P:
Your last screenshot shows one deletion and one insertion -- which is indeed what all "stupid" compare tools do when it actually is not a deletion/insertion but a moved block. The CompareIt screenshot shows movement, but as I said it fails as soon as you change like one character in the moved text.

When you have lots of moved sentences or paragraphs in a long text, and additionally small changes within those moved parts, you have no chance to see what is where with this kind of difference recognition and display.

Code Compare allegedly can detect moved blocks, but only for some programming languages -- not for general text.

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