Forwarding another mail of Doug's that I think was sent to TUHS by mistake.
At 2023-06-13T21:58:51-0400, Douglas McIlroy wrote: > There may be a simple generic way to correct pic's habit of accepting > any set of object modifiers on any object, but obeying only a > compatible subset. > > Pic already collects a bit vector of modifier types attached to the > current object. If that were extended with a few more bits that > designate the object types, the size, B, of the bit vector would be > about 35--an easy fit in one 64-bit word. Then a BxB bit matrix could > record both modifier/modifier incompatibilities and object/modifier > incompatibilities. The collected bit vector needs to be tested against > the matrix once per object definition. > > It seems to be harder to catch duplication of modifiers, requiring > extra code at all points where bits are set. Nevertheless, this kind > of error also merits detection. > > Some questions > > Does anybody think the issue is not worth addressing? > > Is there a better scheme than that suggested above? > > Is the scheme adequate? It would not, for example, catch a three-way > incompatibility that does not entail any pairwise incompatibility, > should such an incompatibility exist. > > Any other thoughts? > > Doug
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