The core of a differential file comparison program,
such as Unix 'diff', is the ability to compute or
approximate the longest common subsequence
of two lists. In response to requests from Pascal
Scheffers and Jean-Claude Wippler for a pure-Tcl
'diff' for wikit, I've developed Tcl code that implements
the Hunt-McIlroy algorithm for longest common
subsequence.

It strikes me that this fits the [chart of proposed
additional list functionality] that Andreas has
placed on the Wiki, and that a natural place to
put it in Tcllib would be as

     [::struct::list lcs $list1 $list2]

But of course, we don't have the ::struct::list
command yet, so I've no framework in which to
fit this.

I'm attaching source code, test suite, and a
draft manual page for the comparison code
to this article for your review.  I'm presuming
that it should fit nicely with feature request
# 577055. But I think that Andreas should
review it and commit if he approves, since he
seems to be the leader for this functionality.

apple

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Created subpackage struct::list in module struct of tcllib,
as per our discussion in the tcler's chat.

File Added - 45770: list.test

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Verified using TDK that list.test has full (line-based)
test coverage of the source code.

File Added - 45769: list.man

File Added - 45768: list.tcl