FA-76931 / Calendar recurrence rules / Open access
Monthly BYSETPOS selection from a weekday set: dup guard · case 01
BYSETPOS=1,-5 in a month with five candidates emits the same day twice.
ROOT CAUSE
Positions that resolve to the same candidate are both appended.
VERIFIED REPAIR
At the dup guard decision use `cand[idx] not in picked`, leaving the other decision sites of the model unchanged.
Unsuccessful approach: The partial repair `cand[idx] != (picked[-1] if picked else None)` only rejects a repeat of the most recently picked day.
Case contract
FREQ=MONTHLY;BYDAY=<weekdays>;BYSETPOS=<positions>. For each month from the dtstart month, the candidate set is every day of the whole month whose weekday is listed, in date order. Positions are 1-based, negative from the end; out-of-range positions are ignored and positions naming the same day yield it once. Selected days are emitted chronologically; days before dtstart are dropped after selection. Return the first count ISO dates.
Why this case matters
Recurring calendar series are expanded into concrete instances for display, reminders and conflict checks.
1 / The failure
Exit 1"""Failure Map reference implementation. Python standard library only."""
import json
import datetime as dt
import calendar
N = 1
observations = []
def solve(dtstart, weekdays, setpos, count):
start = dt.date.fromisoformat(dtstart)
out = []
for k in range(240):
mi = start.month - 1 + k
y, m = start.year + mi // 12, mi % 12 + 1
dim = calendar.monthrange(y, m)[1]
cand = [x for x in [dt.date(y, m, d) for d in range(1, dim + 1)] if x.weekday() in weekdays and x >= dt.date(y, m, 1)]
picked = []
for p in setpos:
idx = p - 1 if p > 0 else len(cand) + p
if 0 <= idx < len(cand) and True:
picked.append(cand[idx])
for d in sorted(picked):
if d < start:
continue
out.append(d.isoformat())
if len(out) >= count:
return out
return out
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[('regression: last weekday of month',
['2024-01-01', [0, 1, 2, 3, 4], [-1], 4],
['2024-01-31', '2024-02-29', '2024-03-29', '2024-04-30']),
('first weekday, dtstart mid-month',
['2024-01-10', [0, 1, 2, 3, 4], [1], 3],
['2024-02-01', '2024-03-01', '2024-04-01']),
('first and last in reverse order',
['2024-03-01', [0, 1, 2, 3, 4], [-1, 1], 4],
['2024-03-01', '2024-03-29', '2024-04-01', '2024-04-30']),
('coinciding positions',
['2024-01-01', [0], [1, -5], 4],
['2024-01-01', '2024-02-05', '2024-03-04', '2024-04-01']),
('three positions with repeat',
['2024-04-01', [2], [1, -1, -5], 5],
['2024-04-03', '2024-04-24', '2024-05-01', '2024-05-29', '2024-06-05']),
('out of range negative', ['2024-01-01', [5, 6], [-7, 1], 3], ['2024-01-06', '2024-01-07', '2024-02-03']),
('out of range positive', ['2024-02-01', [0], [5], 3], ['2024-04-29', '2024-07-29', '2024-09-30'])],
[('first and last in reverse order',
['2024-03-01', [0, 1, 2, 3, 4], [-1, 1], 4],
['2024-03-01', '2024-03-29', '2024-04-01', '2024-04-30']),
('coinciding positions',
['2024-01-01', [0], [1, -5], 4],
['2024-01-01', '2024-02-05', '2024-03-04', '2024-04-01']),
('three positions with repeat',
['2024-04-01', [2], [1, -1, -5], 5],
['2024-04-03', '2024-04-24', '2024-05-01', '2024-05-29', '2024-06-05']),
('out of range negative', ['2024-01-01', [5, 6], [-7, 1], 3], ['2024-01-06', '2024-01-07', '2024-02-03']),
('out of range positive', ['2024-02-01', [0], [5], 3], ['2024-04-29', '2024-07-29', '2024-09-30']),
('second weekend day', ['2024-06-15', [5, 6], [2], 3], ['2024-07-07', '2024-08-04', '2024-09-07']),
('second to last weekday',
['2024-07-01', [0, 1, 2, 3, 4], [-2], 3],
['2024-07-30', '2024-08-29', '2024-09-27'])],
[('three positions with repeat',
['2024-04-01', [2], [1, -1, -5], 5],
['2024-04-03', '2024-04-24', '2024-05-01', '2024-05-29', '2024-06-05']),
('out of range negative', ['2024-01-01', [5, 6], [-7, 1], 3], ['2024-01-06', '2024-01-07', '2024-02-03']),
('out of range positive', ['2024-02-01', [0], [5], 3], ['2024-04-29', '2024-07-29', '2024-09-30']),
('second weekend day', ['2024-06-15', [5, 6], [2], 3], ['2024-07-07', '2024-08-04', '2024-09-07']),
('second to last weekday',
['2024-07-01', [0, 1, 2, 3, 4], [-2], 3],
['2024-07-30', '2024-08-29', '2024-09-27']),
('position 3 of TU,TH mid month',
['2024-09-12', [1, 3], [3, -1], 4],
['2024-09-26', '2024-10-08', '2024-10-31', '2024-11-12']),
('december rollover',
['2024-12-01', [4], [1, -1], 4],
['2024-12-06', '2024-12-27', '2025-01-03', '2025-01-31'])],
[('out of range positive', ['2024-02-01', [0], [5], 3], ['2024-04-29', '2024-07-29', '2024-09-30']),
('second weekend day', ['2024-06-15', [5, 6], [2], 3], ['2024-07-07', '2024-08-04', '2024-09-07']),
('second to last weekday',
['2024-07-01', [0, 1, 2, 3, 4], [-2], 3],
['2024-07-30', '2024-08-29', '2024-09-27']),
('position 3 of TU,TH mid month',
['2024-09-12', [1, 3], [3, -1], 4],
['2024-09-26', '2024-10-08', '2024-10-31', '2024-11-12']),
('december rollover',
['2024-12-01', [4], [1, -1], 4],
['2024-12-06', '2024-12-27', '2025-01-03', '2025-01-31']),
('dtstart equals picked day', ['2024-05-31', [0, 1, 2, 3, 4], [-1], 2], ['2024-05-31', '2024-06-28']),
('regression: last weekday of month',
['2024-01-01', [0, 1, 2, 3, 4], [-1], 4],
['2024-01-31', '2024-02-29', '2024-03-29', '2024-04-30']),
('three positions with repeat',
['2024-04-01', [2], [1, -1, -5], 5],
['2024-04-03', '2024-04-24', '2024-05-01', '2024-05-29', '2024-06-05'])],
[('second to last weekday',
['2024-07-01', [0, 1, 2, 3, 4], [-2], 3],
['2024-07-30', '2024-08-29', '2024-09-27']),
('position 3 of TU,TH mid month',
['2024-09-12', [1, 3], [3, -1], 4],
['2024-09-26', '2024-10-08', '2024-10-31', '2024-11-12']),
('december rollover',
['2024-12-01', [4], [1, -1], 4],
['2024-12-06', '2024-12-27', '2025-01-03', '2025-01-31']),
('dtstart equals picked day', ['2024-05-31', [0, 1, 2, 3, 4], [-1], 2], ['2024-05-31', '2024-06-28']),
('regression: last weekday of month',
['2024-01-01', [0, 1, 2, 3, 4], [-1], 4],
['2024-01-31', '2024-02-29', '2024-03-29', '2024-04-30']),
('first weekday, dtstart mid-month',
['2024-01-10', [0, 1, 2, 3, 4], [1], 3],
['2024-02-01', '2024-03-01', '2024-04-01']),
('first and last in reverse order',
['2024-03-01', [0, 1, 2, 3, 4], [-1, 1], 4],
['2024-03-01', '2024-03-29', '2024-04-01', '2024-04-30']),
('coinciding positions',
['2024-01-01', [0], [1, -5], 4],
['2024-01-01', '2024-02-05', '2024-03-04', '2024-04-01']),
('three positions with repeat',
['2024-04-01', [2], [1, -1, -5], 5],
['2024-04-03', '2024-04-24', '2024-05-01', '2024-05-29', '2024-06-05'])]]
for label, args, expected in fixtures[N-1]:
check(label, solve(*args), expected)
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)
| Boundary fixture | Actual | Expected | Outcome |
|---|---|---|---|
| regression: last weekday of month | ['2024-01-31', '2024-02-29', '2024-03-29', '2024-04-30'] | ['2024-01-31', '2024-02-29', '2024-03-29', '2024-04-30'] | Passed |
| first weekday, dtstart mid-month | ['2024-02-01', '2024-03-01', '2024-04-01'] | ['2024-02-01', '2024-03-01', '2024-04-01'] | Passed |
| first and last in reverse order | ['2024-03-01', '2024-03-29', '2024-04-01', '2024-04-30'] | ['2024-03-01', '2024-03-29', '2024-04-01', '2024-04-30'] | Passed |
| coinciding positions | ['2024-01-01', '2024-01-01', '2024-02-05', '2024-03-04'] | ['2024-01-01', '2024-02-05', '2024-03-04', '2024-04-01'] | Failed |
| three positions with repeat | ['2024-04-03', '2024-04-24', '2024-05-01', '2024-05-01', '2024-05-29'] | ['2024-04-03', '2024-04-24', '2024-05-01', '2024-05-29', '2024-06-05'] | Failed |
| out of range negative | ['2024-01-06', '2024-01-07', '2024-02-03'] | ['2024-01-06', '2024-01-07', '2024-02-03'] | Passed |
| out of range positive | ['2024-04-29', '2024-07-29', '2024-09-30'] | ['2024-04-29', '2024-07-29', '2024-09-30'] | Passed |
SHA-256 / c30ff03748231b9aa96ab7102c961165a679dabd05c30650fa17175fc06842c9
2 / The unsuccessful fix
Exit 1"""Failure Map reference implementation. Python standard library only."""
import json
import datetime as dt
import calendar
N = 1
observations = []
def solve(dtstart, weekdays, setpos, count):
start = dt.date.fromisoformat(dtstart)
out = []
for k in range(240):
mi = start.month - 1 + k
y, m = start.year + mi // 12, mi % 12 + 1
dim = calendar.monthrange(y, m)[1]
cand = [x for x in [dt.date(y, m, d) for d in range(1, dim + 1)] if x.weekday() in weekdays and x >= dt.date(y, m, 1)]
picked = []
for p in setpos:
idx = p - 1 if p > 0 else len(cand) + p
if 0 <= idx < len(cand) and cand[idx] != (picked[-1] if picked else None):
picked.append(cand[idx])
for d in sorted(picked):
if d < start:
continue
out.append(d.isoformat())
if len(out) >= count:
return out
return out
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[('regression: last weekday of month',
['2024-01-01', [0, 1, 2, 3, 4], [-1], 4],
['2024-01-31', '2024-02-29', '2024-03-29', '2024-04-30']),
('first weekday, dtstart mid-month',
['2024-01-10', [0, 1, 2, 3, 4], [1], 3],
['2024-02-01', '2024-03-01', '2024-04-01']),
('first and last in reverse order',
['2024-03-01', [0, 1, 2, 3, 4], [-1, 1], 4],
['2024-03-01', '2024-03-29', '2024-04-01', '2024-04-30']),
('coinciding positions',
['2024-01-01', [0], [1, -5], 4],
['2024-01-01', '2024-02-05', '2024-03-04', '2024-04-01']),
('three positions with repeat',
['2024-04-01', [2], [1, -1, -5], 5],
['2024-04-03', '2024-04-24', '2024-05-01', '2024-05-29', '2024-06-05']),
('out of range negative', ['2024-01-01', [5, 6], [-7, 1], 3], ['2024-01-06', '2024-01-07', '2024-02-03']),
('out of range positive', ['2024-02-01', [0], [5], 3], ['2024-04-29', '2024-07-29', '2024-09-30'])],
[('first and last in reverse order',
['2024-03-01', [0, 1, 2, 3, 4], [-1, 1], 4],
['2024-03-01', '2024-03-29', '2024-04-01', '2024-04-30']),
('coinciding positions',
['2024-01-01', [0], [1, -5], 4],
['2024-01-01', '2024-02-05', '2024-03-04', '2024-04-01']),
('three positions with repeat',
['2024-04-01', [2], [1, -1, -5], 5],
['2024-04-03', '2024-04-24', '2024-05-01', '2024-05-29', '2024-06-05']),
('out of range negative', ['2024-01-01', [5, 6], [-7, 1], 3], ['2024-01-06', '2024-01-07', '2024-02-03']),
('out of range positive', ['2024-02-01', [0], [5], 3], ['2024-04-29', '2024-07-29', '2024-09-30']),
('second weekend day', ['2024-06-15', [5, 6], [2], 3], ['2024-07-07', '2024-08-04', '2024-09-07']),
('second to last weekday',
['2024-07-01', [0, 1, 2, 3, 4], [-2], 3],
['2024-07-30', '2024-08-29', '2024-09-27'])],
[('three positions with repeat',
['2024-04-01', [2], [1, -1, -5], 5],
['2024-04-03', '2024-04-24', '2024-05-01', '2024-05-29', '2024-06-05']),
('out of range negative', ['2024-01-01', [5, 6], [-7, 1], 3], ['2024-01-06', '2024-01-07', '2024-02-03']),
('out of range positive', ['2024-02-01', [0], [5], 3], ['2024-04-29', '2024-07-29', '2024-09-30']),
('second weekend day', ['2024-06-15', [5, 6], [2], 3], ['2024-07-07', '2024-08-04', '2024-09-07']),
('second to last weekday',
['2024-07-01', [0, 1, 2, 3, 4], [-2], 3],
['2024-07-30', '2024-08-29', '2024-09-27']),
('position 3 of TU,TH mid month',
['2024-09-12', [1, 3], [3, -1], 4],
['2024-09-26', '2024-10-08', '2024-10-31', '2024-11-12']),
('december rollover',
['2024-12-01', [4], [1, -1], 4],
['2024-12-06', '2024-12-27', '2025-01-03', '2025-01-31'])],
[('out of range positive', ['2024-02-01', [0], [5], 3], ['2024-04-29', '2024-07-29', '2024-09-30']),
('second weekend day', ['2024-06-15', [5, 6], [2], 3], ['2024-07-07', '2024-08-04', '2024-09-07']),
('second to last weekday',
['2024-07-01', [0, 1, 2, 3, 4], [-2], 3],
['2024-07-30', '2024-08-29', '2024-09-27']),
('position 3 of TU,TH mid month',
['2024-09-12', [1, 3], [3, -1], 4],
['2024-09-26', '2024-10-08', '2024-10-31', '2024-11-12']),
('december rollover',
['2024-12-01', [4], [1, -1], 4],
['2024-12-06', '2024-12-27', '2025-01-03', '2025-01-31']),
('dtstart equals picked day', ['2024-05-31', [0, 1, 2, 3, 4], [-1], 2], ['2024-05-31', '2024-06-28']),
('regression: last weekday of month',
['2024-01-01', [0, 1, 2, 3, 4], [-1], 4],
['2024-01-31', '2024-02-29', '2024-03-29', '2024-04-30']),
('three positions with repeat',
['2024-04-01', [2], [1, -1, -5], 5],
['2024-04-03', '2024-04-24', '2024-05-01', '2024-05-29', '2024-06-05'])],
[('second to last weekday',
['2024-07-01', [0, 1, 2, 3, 4], [-2], 3],
['2024-07-30', '2024-08-29', '2024-09-27']),
('position 3 of TU,TH mid month',
['2024-09-12', [1, 3], [3, -1], 4],
['2024-09-26', '2024-10-08', '2024-10-31', '2024-11-12']),
('december rollover',
['2024-12-01', [4], [1, -1], 4],
['2024-12-06', '2024-12-27', '2025-01-03', '2025-01-31']),
('dtstart equals picked day', ['2024-05-31', [0, 1, 2, 3, 4], [-1], 2], ['2024-05-31', '2024-06-28']),
('regression: last weekday of month',
['2024-01-01', [0, 1, 2, 3, 4], [-1], 4],
['2024-01-31', '2024-02-29', '2024-03-29', '2024-04-30']),
('first weekday, dtstart mid-month',
['2024-01-10', [0, 1, 2, 3, 4], [1], 3],
['2024-02-01', '2024-03-01', '2024-04-01']),
('first and last in reverse order',
['2024-03-01', [0, 1, 2, 3, 4], [-1, 1], 4],
['2024-03-01', '2024-03-29', '2024-04-01', '2024-04-30']),
('coinciding positions',
['2024-01-01', [0], [1, -5], 4],
['2024-01-01', '2024-02-05', '2024-03-04', '2024-04-01']),
('three positions with repeat',
['2024-04-01', [2], [1, -1, -5], 5],
['2024-04-03', '2024-04-24', '2024-05-01', '2024-05-29', '2024-06-05'])]]
for label, args, expected in fixtures[N-1]:
check(label, solve(*args), expected)
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)
| Boundary fixture | Actual | Expected | Outcome |
|---|---|---|---|
| regression: last weekday of month | ['2024-01-31', '2024-02-29', '2024-03-29', '2024-04-30'] | ['2024-01-31', '2024-02-29', '2024-03-29', '2024-04-30'] | Passed |
| first weekday, dtstart mid-month | ['2024-02-01', '2024-03-01', '2024-04-01'] | ['2024-02-01', '2024-03-01', '2024-04-01'] | Passed |
| first and last in reverse order | ['2024-03-01', '2024-03-29', '2024-04-01', '2024-04-30'] | ['2024-03-01', '2024-03-29', '2024-04-01', '2024-04-30'] | Passed |
| coinciding positions | ['2024-01-01', '2024-02-05', '2024-03-04', '2024-04-01'] | ['2024-01-01', '2024-02-05', '2024-03-04', '2024-04-01'] | Passed |
| three positions with repeat | ['2024-04-03', '2024-04-24', '2024-05-01', '2024-05-01', '2024-05-29'] | ['2024-04-03', '2024-04-24', '2024-05-01', '2024-05-29', '2024-06-05'] | Failed |
| out of range negative | ['2024-01-06', '2024-01-07', '2024-02-03'] | ['2024-01-06', '2024-01-07', '2024-02-03'] | Passed |
| out of range positive | ['2024-04-29', '2024-07-29', '2024-09-30'] | ['2024-04-29', '2024-07-29', '2024-09-30'] | Passed |
SHA-256 / 3e90c326a7a92367e824ce0ee4972fe75d4ec030a4e5cf18e41484524c84f1c6
3 / The verified repair
Exit 0"""Failure Map reference implementation. Python standard library only."""
import json
import datetime as dt
import calendar
N = 1
observations = []
def solve(dtstart, weekdays, setpos, count):
start = dt.date.fromisoformat(dtstart)
out = []
for k in range(240):
mi = start.month - 1 + k
y, m = start.year + mi // 12, mi % 12 + 1
dim = calendar.monthrange(y, m)[1]
cand = [x for x in [dt.date(y, m, d) for d in range(1, dim + 1)] if x.weekday() in weekdays and x >= dt.date(y, m, 1)]
picked = []
for p in setpos:
idx = p - 1 if p > 0 else len(cand) + p
if 0 <= idx < len(cand) and cand[idx] not in picked:
picked.append(cand[idx])
for d in sorted(picked):
if d < start:
continue
out.append(d.isoformat())
if len(out) >= count:
return out
return out
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[('regression: last weekday of month',
['2024-01-01', [0, 1, 2, 3, 4], [-1], 4],
['2024-01-31', '2024-02-29', '2024-03-29', '2024-04-30']),
('first weekday, dtstart mid-month',
['2024-01-10', [0, 1, 2, 3, 4], [1], 3],
['2024-02-01', '2024-03-01', '2024-04-01']),
('first and last in reverse order',
['2024-03-01', [0, 1, 2, 3, 4], [-1, 1], 4],
['2024-03-01', '2024-03-29', '2024-04-01', '2024-04-30']),
('coinciding positions',
['2024-01-01', [0], [1, -5], 4],
['2024-01-01', '2024-02-05', '2024-03-04', '2024-04-01']),
('three positions with repeat',
['2024-04-01', [2], [1, -1, -5], 5],
['2024-04-03', '2024-04-24', '2024-05-01', '2024-05-29', '2024-06-05']),
('out of range negative', ['2024-01-01', [5, 6], [-7, 1], 3], ['2024-01-06', '2024-01-07', '2024-02-03']),
('out of range positive', ['2024-02-01', [0], [5], 3], ['2024-04-29', '2024-07-29', '2024-09-30'])],
[('first and last in reverse order',
['2024-03-01', [0, 1, 2, 3, 4], [-1, 1], 4],
['2024-03-01', '2024-03-29', '2024-04-01', '2024-04-30']),
('coinciding positions',
['2024-01-01', [0], [1, -5], 4],
['2024-01-01', '2024-02-05', '2024-03-04', '2024-04-01']),
('three positions with repeat',
['2024-04-01', [2], [1, -1, -5], 5],
['2024-04-03', '2024-04-24', '2024-05-01', '2024-05-29', '2024-06-05']),
('out of range negative', ['2024-01-01', [5, 6], [-7, 1], 3], ['2024-01-06', '2024-01-07', '2024-02-03']),
('out of range positive', ['2024-02-01', [0], [5], 3], ['2024-04-29', '2024-07-29', '2024-09-30']),
('second weekend day', ['2024-06-15', [5, 6], [2], 3], ['2024-07-07', '2024-08-04', '2024-09-07']),
('second to last weekday',
['2024-07-01', [0, 1, 2, 3, 4], [-2], 3],
['2024-07-30', '2024-08-29', '2024-09-27'])],
[('three positions with repeat',
['2024-04-01', [2], [1, -1, -5], 5],
['2024-04-03', '2024-04-24', '2024-05-01', '2024-05-29', '2024-06-05']),
('out of range negative', ['2024-01-01', [5, 6], [-7, 1], 3], ['2024-01-06', '2024-01-07', '2024-02-03']),
('out of range positive', ['2024-02-01', [0], [5], 3], ['2024-04-29', '2024-07-29', '2024-09-30']),
('second weekend day', ['2024-06-15', [5, 6], [2], 3], ['2024-07-07', '2024-08-04', '2024-09-07']),
('second to last weekday',
['2024-07-01', [0, 1, 2, 3, 4], [-2], 3],
['2024-07-30', '2024-08-29', '2024-09-27']),
('position 3 of TU,TH mid month',
['2024-09-12', [1, 3], [3, -1], 4],
['2024-09-26', '2024-10-08', '2024-10-31', '2024-11-12']),
('december rollover',
['2024-12-01', [4], [1, -1], 4],
['2024-12-06', '2024-12-27', '2025-01-03', '2025-01-31'])],
[('out of range positive', ['2024-02-01', [0], [5], 3], ['2024-04-29', '2024-07-29', '2024-09-30']),
('second weekend day', ['2024-06-15', [5, 6], [2], 3], ['2024-07-07', '2024-08-04', '2024-09-07']),
('second to last weekday',
['2024-07-01', [0, 1, 2, 3, 4], [-2], 3],
['2024-07-30', '2024-08-29', '2024-09-27']),
('position 3 of TU,TH mid month',
['2024-09-12', [1, 3], [3, -1], 4],
['2024-09-26', '2024-10-08', '2024-10-31', '2024-11-12']),
('december rollover',
['2024-12-01', [4], [1, -1], 4],
['2024-12-06', '2024-12-27', '2025-01-03', '2025-01-31']),
('dtstart equals picked day', ['2024-05-31', [0, 1, 2, 3, 4], [-1], 2], ['2024-05-31', '2024-06-28']),
('regression: last weekday of month',
['2024-01-01', [0, 1, 2, 3, 4], [-1], 4],
['2024-01-31', '2024-02-29', '2024-03-29', '2024-04-30']),
('three positions with repeat',
['2024-04-01', [2], [1, -1, -5], 5],
['2024-04-03', '2024-04-24', '2024-05-01', '2024-05-29', '2024-06-05'])],
[('second to last weekday',
['2024-07-01', [0, 1, 2, 3, 4], [-2], 3],
['2024-07-30', '2024-08-29', '2024-09-27']),
('position 3 of TU,TH mid month',
['2024-09-12', [1, 3], [3, -1], 4],
['2024-09-26', '2024-10-08', '2024-10-31', '2024-11-12']),
('december rollover',
['2024-12-01', [4], [1, -1], 4],
['2024-12-06', '2024-12-27', '2025-01-03', '2025-01-31']),
('dtstart equals picked day', ['2024-05-31', [0, 1, 2, 3, 4], [-1], 2], ['2024-05-31', '2024-06-28']),
('regression: last weekday of month',
['2024-01-01', [0, 1, 2, 3, 4], [-1], 4],
['2024-01-31', '2024-02-29', '2024-03-29', '2024-04-30']),
('first weekday, dtstart mid-month',
['2024-01-10', [0, 1, 2, 3, 4], [1], 3],
['2024-02-01', '2024-03-01', '2024-04-01']),
('first and last in reverse order',
['2024-03-01', [0, 1, 2, 3, 4], [-1, 1], 4],
['2024-03-01', '2024-03-29', '2024-04-01', '2024-04-30']),
('coinciding positions',
['2024-01-01', [0], [1, -5], 4],
['2024-01-01', '2024-02-05', '2024-03-04', '2024-04-01']),
('three positions with repeat',
['2024-04-01', [2], [1, -1, -5], 5],
['2024-04-03', '2024-04-24', '2024-05-01', '2024-05-29', '2024-06-05'])]]
for label, args, expected in fixtures[N-1]:
check(label, solve(*args), expected)
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)
| Boundary fixture | Actual | Expected | Outcome |
|---|---|---|---|
| regression: last weekday of month | ['2024-01-31', '2024-02-29', '2024-03-29', '2024-04-30'] | ['2024-01-31', '2024-02-29', '2024-03-29', '2024-04-30'] | Passed |
| first weekday, dtstart mid-month | ['2024-02-01', '2024-03-01', '2024-04-01'] | ['2024-02-01', '2024-03-01', '2024-04-01'] | Passed |
| first and last in reverse order | ['2024-03-01', '2024-03-29', '2024-04-01', '2024-04-30'] | ['2024-03-01', '2024-03-29', '2024-04-01', '2024-04-30'] | Passed |
| coinciding positions | ['2024-01-01', '2024-02-05', '2024-03-04', '2024-04-01'] | ['2024-01-01', '2024-02-05', '2024-03-04', '2024-04-01'] | Passed |
| three positions with repeat | ['2024-04-03', '2024-04-24', '2024-05-01', '2024-05-29', '2024-06-05'] | ['2024-04-03', '2024-04-24', '2024-05-01', '2024-05-29', '2024-06-05'] | Passed |
| out of range negative | ['2024-01-06', '2024-01-07', '2024-02-03'] | ['2024-01-06', '2024-01-07', '2024-02-03'] | Passed |
| out of range positive | ['2024-04-29', '2024-07-29', '2024-09-30'] | ['2024-04-29', '2024-07-29', '2024-09-30'] | Passed |
SHA-256 / 61c5314eafd4567bdb168e09f1a89eca0f56e7ecc2aca46570d477f2dc0e2d26
Verification & scope
Stipulated, bounded recurrence-expansion model evaluated offline on explicit fixtures; it is not a complete iCalendar implementation and makes no claim of standards conformance. This reproducer isolates one failure mechanism. Results cover the supplied fixtures. Variants within a family share a test contract and should remain grouped when constructing evaluation splits. Related mechanisms with a shared evaluation_group must also remain together; these controlled models are not independent production incidents.
Observations recorded using Python 3.12.14 at 2026-09-29T14:49:20.678240+00:00.
Case digest / ebde19cc71813f00ba80ba829ed5eee16b95dc275b97e335f4a84a54e2d3b76c