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[Joseph Osborn <joe.osborn AT me.com>]

A common feature of languages with pattern-matching (even K!) is the 
"don't-care" variable "_", which matches anything, each instance of which is 
fresh. It doesn't seem like the UNIFICATION module supports these wildcards, 
so here's a little patch that puts them in (in a somewhat ad hoc way 
explicitly for unification, rather than by doing that formal replacement of 
terms by fresh terms, because it seemed simpler).

Languages which want it should have a line like the following, though of 
course "_" is only an example:

> syntax SomethingThatGetsUnified ::= "_" [onlyLabel, klabel($dontcare)]


There's probably a more K-like way to do that attribute ([dontcare] or 
[wildcard] or something?), but that's all I know how to do right now. All the 
LOGIK examples I tried (and those of my own language) seem to still work, but 
I have not tested exhaustively.

Diff's attached, I hope it doesn't get scrubbed by the listserv!

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