The differences between Spirit.X3 and Parser need to be made much more
clear by the
documentation, by which I mean:
Spirit X3 has rules that do not compose well — the attributes produced
by a rule can change depending on the context in which you use the rule.
Spirit X3 is missing many of the convenient interfaces to parsers that
Spirit 2 had. For instance, you cannot add
parameters to a parser.
All versions of Spirit have Unicode support, but it is quite difficult
to get working.
These need code samples showing the limitations of X3 and how Parser
actually solves them. I think many,
myself included, aren't overwhelmingly clear on what these differences are
and how Parser solves them
and why this is a good thing.
From Christian Mazakas in the Boost review: