Re: [PATCH v2] make diff --color-words customizable

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On Sat, 10 Jan 2009, Jakub Narebski wrote:

> On Sat, 10 Jan 2009, Johannes Schindelin wrote:
> > On Sat, 10 Jan 2009, Jakub Narebski wrote:
> > > Thomas Rast wrote:
> > > 
> > > > --color-words works (and always worked) by splitting words onto one
> > > > line each, and using the normal line-diff machinery to get a word
> > > > diff. 
> > > 
> > > Cannot we generalize diff machinery / use underlying LCS diff engine
> > > instead of going through line diff?
> > 
> > What do you think we're doing?  libxdiff is pretty hardcoded to newlines.  
> > That's why we're substituting non-word characters with newlines.
> 
> Isn't Meyers algorithm used by libxdiff based on LCS, largest common
> subsequence, and doesn't it generate from the mathematical point of
> view "diff" between two sequences (two arrays) which just happen to
> be lines? It is a bit strange that libxdiff doesn't export its low
> level algorithm...

The core doesn't know anything about lines. Only pre-processing (setting 
up the hash by tokenizing the input) and post-processing (adding '\n' to 
the end of each token), knows about newlines. Memory consumption would 
increase significantly though, since there is a per-token cost, and a 
word-based diff will create more of them WRT the same input.


- Davide


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