Le 21/04/2022 à 12:58, David Kastrup a écrit :
My personal take on this would move the magic out of the normal reach of users. You get (*start-column*) and (*end-column*) which you can use for accessing the respective fluids but the function *start-column* does not merely access %start-column but it also registers the associated impurity for the sake of caching.
Absolutely, I don't want to make the fluids accessible to anything outside of the property infrastructure. *start-column* (or whatever name) is an Assumption object. Assumption is a smob type defining a call () smob procedure. That way, you can have (*start-column*) and (under-assumptions ((*start-column* 0)) ...) and both of these use the fluid as well as other internal members of the assumption without ever making them accessible. For the latter, the under-assumptions macro invocation translates to (ly:run-under-assumption *start-column* 0 (lambda () ...)) which makes the interface completely opaque/encapsulated.
