[darcs-devel] [patch1844] automatically specialize merging and equality for sequences of patches with identity

[Ben Franksen]

Ben Franksen <ben.franksen at online.de> added the comment:

I just realized that semantic equality for patches and patch 
sequences is not sufficient. It would be enough for darcs itself, 
but many /properties/ can only be expressed via structural equality. 
In particular, any property /about/ semantic equality must refer to 
the underlying structural equality or be vacuous. Similarly, the 
usual read/show roundtrip properties should be expressed with 
structural comparison else we risk testing only that the contained 
PatchIds are correctly roundtripped.

The recent introduction of NamedPrim, class Ident, and now class 
Sequence in this bundle, has made it rather obvious that we cannot 
continue to be unclear which sort of equality we mean. Our current 
=\/= and =/\= operators are clearly meant to be semantic, so we need 
new "operators" (functions, methods) to express structural equality.

This means that we either need to add more methods to class Eq2 or 
introcude a new class.

Any ideas?

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