Path: news.eternal-september.org!eternal-september.org!.POSTED!not-for-mail
From: Rich <rich@example.invalid>
Newsgroups: comp.lang.tcl
Subject: Re: diff and patch
Date: Tue, 17 Jun 2025 22:36:55 -0000 (UTC)
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Mark Summerfield <m.n.summerfield@gmail.com> wrote:
> I want these functions:
> 
>     proc diff {old new} -> # diff data "ddata"
>     proc patch {old ddata} -> # new
> 
> where old and new are strings.
> 
> I thought the Tcllib's rcs module could do this but I can't figure it out.
> 
> Is this possible using the rcs module or using the struct::list module's 
> LCS functions?

The core of the diff algorithm is LCS.  You want the LCS functions from 
struct::list.

But, you don't get a "diff" from the LCS procs, you get the LCS data, 
you then have to convert that into a "diff" format of your choice.

You likely want to look at the various "diff in tcl" pages on the wiki.  
A starting point: https://wiki.tcl-lang.org/page/diff+in+Tcl