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open Colitur_kernel
(* Step 1: the observed celebration's own proper.
Step 2: the day's own temporal slug.
Step 3: a weekday whose own slug has no entry says the preceding Sunday's
Mass -- see the implementation comment on that branch in [readings] for
the termination argument and why it is the Sunday's TEMPORAL, not
observed, identity.
Nothing here encodes "Lent has daily propers": the presence of an entry in
[lectionary] is the sole discriminator -- this function does not branch on
season, rank, or any other field to decide whether a temporal slug "ought"
to have its own Mass.
The WARRANT for that shape is lectio's own observed behaviour only, not a
confirmed Missal citation: Lent 1 Monday returns its own Ezech 34:11-16,
while Advent, Christmas and post-Pentecost Mondays return their Sunday's
Mass, in both streams. docs/research/rules-register.md records this
openly as unconfirmed against the primary source ("EF reading-selection
rules ... Have lectio's behaviour; confirm against the Missal's
ferial-Mass rubrics when coding") -- that confirmation has not been done;
do not read this comment as citing RG/the Missal for the SELECTION rule
itself, only [Lectionary.find]'s presence-or-absence as the mechanism. *)
(* Days from a given weekday back to the preceding Sunday. Sunday itself
yields 0, which is why step 3 must guard on it -- see [readings] below. *)
let days_since_sunday : Date.weekday -> int = function
| Date.Sun -> 0
| Date.Mon -> 1
| Date.Tue -> 2
| Date.Wed -> 3
| Date.Thu -> 4
| Date.Fri -> 5
| Date.Sat -> 6
let readings ~lectionary ~observed ~temporal ~date ~temporal_at =
match observed.Celebration.citations with
| _ :: _ as cs -> cs
| [] -> (
match Lectionary.find lectionary temporal.Temporal.office.Celebration.slug with
| Some cs -> cs
| None -> (
(* Step 3: a feria with no proper of its own says the preceding
Sunday's Mass. WARRANT is the same as step 2's -- lectio's own
observed behaviour, not a confirmed Missal citation: this is the
rule lectio hard-codes as data on the four Advent ferias
(Advent II's readings copied verbatim onto the following
Monday-Saturday) and leaves absent on the other slugs this step
now also reaches; docs/research/rules-register.md already
records the ferial-Mass selection rule itself as unconfirmed
against the primary source.
Guarded on weekday, but NOT because a Sunday reaching this
branch would loop (fix round 1, coordinator review: the
original comment here claimed exactly that, and it was wrong).
[readings] is not recursive -- step 3's fallback is one flat
[Lectionary.find], never a re-entrant call into [readings] --
so without the guard, [days_since_sunday Sun = 0] would just
repeat the SAME [Lectionary.find] step 2 already ran and
already got [None] from (same pure inputs, same date), and
return [] once, normally. The chain as a whole terminates
because every step either consults data (a lookup) or, here,
a strictly EARLIER date via [temporal_at] -- no step ever calls
back into [readings] itself, so there is no recursion anywhere
in this function for a cycle to form in the first place. The
real reason for the guard is simpler: a Sunday has no
PRECEDING Sunday to resume -- consulting itself would be
meaningless (it would re-ask the question step 2 just
answered), not dangerous, so the guard exists to make that
intent explicit rather than to prevent a runaway loop that was
never actually possible.
The preceding Sunday's TEMPORAL slug, never its observed one:
the rubric is the preceding Sunday's Mass even in a year when a
feast displaced that Sunday from being observed (see
test_step3_uses_temporal_not_observed). [temporal_at] gives the
temporal identity of any date, so the Sunday is reached by date
arithmetic and a fresh call to the temporal cycle -- never by
string surgery on [own_slug]: the slug shapes are genuinely
inconsistent across seasons (e.g. [ef-advent-sunday-1] versus
[ef-advent-1-monday], the week number on opposite sides of the
season name), so deriving one from the other textually would be
a latent bug the moment a season's naming convention differs. *)
let offset = days_since_sunday temporal.Temporal.weekday in
if offset = 0 then []
else
let sunday = Date.add_days date (-offset) in
let sunday_temporal = temporal_at sunday in
match
Lectionary.find lectionary sunday_temporal.Temporal.office.Celebration.slug
with
| Some cs -> cs
| None -> []))
|
