Infix synonym for
refines.
You might think this should be
=<=, so it looks kind of
like a funny subset operator, with
A =<= B meaning "the
result-set of A is a subset of the result-set of B". Unfortunately you
would be wrong. The operator used in the literature for refinement has
the open end pointing at the LESS general term and the closed end at
the MORE general term. It is read as "is refined by", not "refines".
So for consistency with the literature, the open end of
=>= points at the less general term, and the closed end at
the more general term, to give the same argument order as
refines.