3 ms·
I think there is a problem with the meaning of the '==' sign here. You are using algebraic notation where we are really dealing with ordered sets and their memb
by Archelaos 5y ago
I think there is a problem with the meaning of the '==' sign here. You are using algebraic notation where we are really dealing with ordered sets and their members. So '==' meaning equivalence is not very useful here. 'Date("192X-XX-XX")' denotes the interval [Date("1920-01-01") ... Date("1929-12-31")]. So '<', '>', '==' should best be defined in terms of ordered sets:
d < I means date d is before any date in I
d > I means date d is after any date in I
d == I means date d is included in I
This would make your last equation 'true'.
If instead you rather prefer to leave 'd == I' undefined, I could hardly find it convincing that you assign a truth value to '<='.
- vharuck 5y agoI've corrected the first date comparison to be ">=". Thanks for pointing that out. >'Date("192X-XX-XX")' denotes the interval [Date("1920-01-01") ... Date("1929-12-31")] The partial date is not the set, but a single date that is in a set. There is notation for sets of dates: # Each means a single day in the 1920s 192X-XX-XX [1920-01-01..1929-12-31] # A collection of all days in the 1920s {1920-01-01..1929-12-31}