Stefan Monnier <monnier@iro.umontreal.ca> writes:

> There wasn't enough space in the margin for it, sorry,

Very funny, ehm -

here is a proof of concept.  It is not exactly what you suggested: you
have to declare dependencies explicitly (I think this would even make
code better readable).  But dependencies do not need to be sscells - I
made it so that dependencies can be arbitrary expressions (this includes
variables as major case), and an equivalence predicate for testing can
be optionally specified, defaulting to #'eq.

You can make an sscell B depend on the value of sscell A by making B
depend on the expression (sscell-get A).

These sscell objects are a generalization of thunks as in thunk.el, and
sscell-let is a generalization of thunk-let.