You wrote "In general reversed/converse has no meaning for block."

That's entirely an artefact of representing blocks of different

arities by the same class.�� In my own Smalltalk, NiladicBlock,

MonadicBlock, DyadicBlock, ... are different classes.�� To put it

another way, your statement has exactly the same status as

"In general #value:value: has no meaning for block."

#converse has meaning for *all* DyadicBlocks, it is the

combinator flip f x y = f y x.�� For that matter, it could

be generalised to all blocks of arity >= 2 as

[:a1 :a2 ... :an | body] converse

=> [:a2 :a1 ... :an | body]

i.e., flip the first two arguments.

My original implementation of #converse was

DyadicBlock

�� methods for: 'combinators'

������ converse

���������� ^[:x :y | self value: y value: x]

������ "other combinators"

With a suitable set of combinators, I can do things like

#name ascending thenBy: #age descending thenBy: #weight ascending nilsFirst