# temporal.rel — the affine algebra of time, as data.
#
# An Instant is a POINT and a Duration is a DISPLACEMENT. Every rule below
# follows from that, and the set is closed because there are only two kinds of
# thing: you may add a displacement to a point, subtract two points to get a
# displacement, and combine displacements. Nothing else is meaningful.
#
# The emitter records which illegal combination it saw; this file says what that
# means and how to say it.
#
#   <kind> means <message>

instant_plus_instant   means Instant + Instant is not allowed — a point plus a point is not a point. Subtract them for a Duration, or add a Duration.
duration_plus_int      means Duration + Int is not allowed — an Int carries no unit. Use duration_seconds(n) or N.seconds.
duration_minus_int     means Duration - Int is not allowed — an Int carries no unit.
instant_cmp_duration   means Instant < Duration is not allowed — a point and a displacement are not on the same scale.
duration_cmp_instant   means Duration < Instant is not allowed — a displacement and a point are not on the same scale.
caltime_plus_caltime   means CalendarTime + CalendarTime is not allowed — a CalendarTime already projects an Instant under a Calendar. Use cal_to_instant first.