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FA-59521 / Subscription proration billing / Open access

Prorated amounts in currency minor units: negative display split · case 01

Negative prorations display garbled amounts such as --2.50.

Verified by executionVariant 1 · 9 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

Major and minor parts are split from the signed value, so floor division moves negatives down a unit.

THE FAILURE

Major and minor parts are split from the signed value, so floor division moves negatives down a unit.

Unsuccessful approach: The attempt keeps the sign inside the major part while also printing the separate sign.

Case contract

Input {price (signed minor units), currency, num, den}. Exponents: USD 2, EUR 2, JPY 0, KWD 3, CLP 0. Amount = price*num/den rounded half away from zero. Display: zero-exponent currencies show an integer; others show sign, major units, a dot and exactly exponent digits, then a space and the code. Return {minor, display}.

Why this case matters

Prorated amounts must round and render in each currency's own minor-unit precision, including credits.

1 / The failure

Exit 1
"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(x):
    exp = {'USD': 2, 'EUR': 2, 'JPY': 0, 'KWD': 3, 'CLP': 0}[x['currency']]
    n = x['price'] * x['num']
    v = (abs(n) * 2 + x['den']) // (2 * x['den'])
    v = v if n >= 0 else -v
    if exp == 0:
        disp = str(v)
    else:
        sign = '-' if v < 0 else ''
        q, r = divmod(v, 10 ** exp)
        disp = '%s%d.%0*d' % (sign, q, exp, r)
    return {'minor': v, 'display': disp + ' ' + x['currency']}
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[('regression', {'price': -6310, 'currency': 'EUR', 'num': 23, 'den': 31}, {'minor': -4682, 'display': '-46.82 EUR'}), ('regression (boundary)', {'price': -3, 'currency': 'USD', 'num': 1, 'den': 2}, {'minor': -2, 'display': '-0.02 USD'}), ('partial-repair probe', {'price': -357324, 'currency': 'USD', 'num': 19, 'den': 30}, {'minor': -226305, 'display': '-2263.05 USD'}), ('partial-repair probe', {'price': -927642, 'currency': 'KWD', 'num': 9, 'den': 31}, {'minor': -269315, 'display': '-269.315 KWD'}), ('boundary control', {'price': 5, 'currency': 'JPY', 'num': 1, 'den': 2}, {'minor': 3, 'display': '3 JPY'}), ('normal control', {'price': 63, 'currency': 'JPY', 'num': 925, 'den': 1000}, {'minor': 58, 'display': '58 JPY'}), ('normal control', {'price': 59, 'currency': 'JPY', 'num': 2, 'den': 4}, {'minor': 30, 'display': '30 JPY'}), ('normal control', {'price': 26, 'currency': 'KWD', 'num': 3, 'den': 31}, {'minor': 3, 'display': '0.003 KWD'}), ('normal control', {'price': -18, 'currency': 'JPY', 'num': 81, 'den': 365}, {'minor': -4, 'display': '-4 JPY'})], [('regression', {'price': -357324, 'currency': 'USD', 'num': 19, 'den': 30}, {'minor': -226305, 'display': '-2263.05 USD'}), ('regression (boundary)', {'price': -7, 'currency': 'KWD', 'num': 1, 'den': 2}, {'minor': -4, 'display': '-0.004 KWD'}), ('partial-repair probe', {'price': -927642, 'currency': 'KWD', 'num': 9, 'den': 31}, {'minor': -269315, 'display': '-269.315 KWD'}), ('partial-repair probe', {'price': -70708, 'currency': 'EUR', 'num': 787, 'den': 1000}, {'minor': -55647, 'display': '-556.47 EUR'}), ('boundary control', {'price': 5, 'currency': 'JPY', 'num': 1, 'den': 2}, {'minor': 3, 'display': '3 JPY'}), ('normal control', {'price': -48, 'currency': 'JPY', 'num': 0, 'den': 4}, {'minor': 0, 'display': '0 JPY'}), ('normal control', {'price': -79, 'currency': 'JPY', 'num': 200, 'den': 365}, {'minor': -43, 'display': '-43 JPY'}), ('normal control', {'price': -93, 'currency': 'EUR', 'num': 0, 'den': 2}, {'minor': 0, 'display': '0.00 EUR'}), ('normal control', {'price': 464209, 'currency': 'EUR', 'num': 10, 'den': 30}, {'minor': 154736, 'display': '1547.36 EUR'})], [('regression', {'price': -927642, 'currency': 'KWD', 'num': 9, 'den': 31}, {'minor': -269315, 'display': '-269.315 KWD'}), ('regression (boundary)', {'price': -105, 'currency': 'EUR', 'num': 1, 'den': 2}, {'minor': -53, 'display': '-0.53 EUR'}), ('partial-repair probe', {'price': -686147, 'currency': 'EUR', 'num': 2, 'den': 31}, {'minor': -44268, 'display': '-442.68 EUR'}), ('partial-repair probe', {'price': -272855, 'currency': 'KWD', 'num': 798, 'den': 1000}, {'minor': -217738, 'display': '-217.738 KWD'}), ('boundary control', {'price': 5, 'currency': 'JPY', 'num': 1, 'den': 2}, {'minor': 3, 'display': '3 JPY'}), ('normal control', {'price': 61, 'currency': 'JPY', 'num': 50, 'den': 365}, {'minor': 8, 'display': '8 JPY'}), ('normal control', {'price': 675691, 'currency': 'KWD', 'num': 214, 'den': 365}, {'minor': 396159, 'display': '396.159 KWD'}), ('normal control', {'price': 95, 'currency': 'USD', 'num': 25, 'den': 30}, {'minor': 79, 'display': '0.79 USD'}), ('normal control', {'price': 553663, 'currency': 'USD', 'num': 138, 'den': 365}, {'minor': 209330, 'display': '2093.30 USD'})], [('regression', {'price': -70708, 'currency': 'EUR', 'num': 787, 'den': 1000}, {'minor': -55647, 'display': '-556.47 EUR'}), ('regression', {'price': -6310, 'currency': 'EUR', 'num': 23, 'den': 31}, {'minor': -4682, 'display': '-46.82 EUR'}), ('partial-repair probe', {'price': -940440, 'currency': 'EUR', 'num': 894, 'den': 1000}, {'minor': -840753, 'display': '-8407.53 EUR'}), ('partial-repair probe', {'price': -345259, 'currency': 'EUR', 'num': 4, 'den': 4}, {'minor': -345259, 'display': '-3452.59 EUR'}), ('boundary control', {'price': 5, 'currency': 'JPY', 'num': 1, 'den': 2}, {'minor': 3, 'display': '3 JPY'}), ('normal control', {'price': 86, 'currency': 'EUR', 'num': 0, 'den': 2}, {'minor': 0, 'display': '0.00 EUR'}), ('normal control', {'price': 21, 'currency': 'JPY', 'num': 3, 'den': 30}, {'minor': 2, 'display': '2 JPY'}), ('normal control', {'price': 127, 'currency': 'JPY', 'num': 0, 'den': 2}, {'minor': 0, 'display': '0 JPY'}), ('normal control', {'price': 248141, 'currency': 'EUR', 'num': 187, 'den': 365}, {'minor': 127130, 'display': '1271.30 EUR'})], [('regression', {'price': -686147, 'currency': 'EUR', 'num': 2, 'den': 31}, {'minor': -44268, 'display': '-442.68 EUR'}), ('regression', {'price': -35, 'currency': 'KWD', 'num': 30, 'den': 30}, {'minor': -35, 'display': '-0.035 KWD'}), ('partial-repair probe', {'price': -799709, 'currency': 'USD', 'num': 177, 'den': 365}, {'minor': -387804, 'display': '-3878.04 USD'}), ('partial-repair probe', {'price': -45094, 'currency': 'EUR', 'num': 282, 'den': 365}, {'minor': -34840, 'display': '-348.40 EUR'}), ('boundary control', {'price': 5, 'currency': 'JPY', 'num': 1, 'den': 2}, {'minor': 3, 'display': '3 JPY'}), ('normal control', {'price': 8, 'currency': 'EUR', 'num': 25, 'den': 31}, {'minor': 6, 'display': '0.06 EUR'}), ('normal control', {'price': -19, 'currency': 'EUR', 'num': 0, 'den': 31}, {'minor': 0, 'display': '0.00 EUR'}), ('normal control', {'price': -70, 'currency': 'JPY', 'num': 209, 'den': 365}, {'minor': -40, 'display': '-40 JPY'}), ('normal control', {'price': 26512, 'currency': 'USD', 'num': 248, 'den': 365}, {'minor': 18014, 'display': '180.14 USD'})]]
for i, (label, args, expected) in enumerate(fixtures[N-1]):
    check("%s %d" % (label, i), 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 fixtureActualExpectedOutcome
regression 0{'display': '--47.18 EUR', 'minor': -4682}{'display': '-46.82 EUR', 'minor': -4682}Failed
regression (boundary) 1{'display': '--1.98 USD', 'minor': -2}{'display': '-0.02 USD', 'minor': -2}Failed
partial-repair probe 2{'display': '--2264.95 USD', 'minor': -226305}{'display': '-2263.05 USD', 'minor': -226305}Failed
partial-repair probe 3{'display': '--270.685 KWD', 'minor': -269315}{'display': '-269.315 KWD', 'minor': -269315}Failed
boundary control 4{'display': '3 JPY', 'minor': 3}{'display': '3 JPY', 'minor': 3}Passed
normal control 5{'display': '58 JPY', 'minor': 58}{'display': '58 JPY', 'minor': 58}Passed
normal control 6{'display': '30 JPY', 'minor': 30}{'display': '30 JPY', 'minor': 30}Passed
normal control 7{'display': '0.003 KWD', 'minor': 3}{'display': '0.003 KWD', 'minor': 3}Passed
normal control 8{'display': '-4 JPY', 'minor': -4}{'display': '-4 JPY', 'minor': -4}Passed

SHA-256 / 5dddf60c0c34bbdc3b657237503d66754e6f0ef3387fce6ca7a4f012d7ba8c9e

2 / The unsuccessful fix

Exit 1
"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(x):
    exp = {'USD': 2, 'EUR': 2, 'JPY': 0, 'KWD': 3, 'CLP': 0}[x['currency']]
    n = x['price'] * x['num']
    v = (abs(n) * 2 + x['den']) // (2 * x['den'])
    v = v if n >= 0 else -v
    if exp == 0:
        disp = str(v)
    else:
        sign = '-' if v < 0 else ''
        q, r = divmod(v, 10 ** exp) if v >= 0 else (-(abs(v) // 10 ** exp), abs(v) % 10 ** exp)
        disp = '%s%d.%0*d' % (sign, q, exp, r)
    return {'minor': v, 'display': disp + ' ' + x['currency']}
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[('regression', {'price': -6310, 'currency': 'EUR', 'num': 23, 'den': 31}, {'minor': -4682, 'display': '-46.82 EUR'}), ('regression (boundary)', {'price': -3, 'currency': 'USD', 'num': 1, 'den': 2}, {'minor': -2, 'display': '-0.02 USD'}), ('partial-repair probe', {'price': -357324, 'currency': 'USD', 'num': 19, 'den': 30}, {'minor': -226305, 'display': '-2263.05 USD'}), ('partial-repair probe', {'price': -927642, 'currency': 'KWD', 'num': 9, 'den': 31}, {'minor': -269315, 'display': '-269.315 KWD'}), ('boundary control', {'price': 5, 'currency': 'JPY', 'num': 1, 'den': 2}, {'minor': 3, 'display': '3 JPY'}), ('normal control', {'price': 63, 'currency': 'JPY', 'num': 925, 'den': 1000}, {'minor': 58, 'display': '58 JPY'}), ('normal control', {'price': 59, 'currency': 'JPY', 'num': 2, 'den': 4}, {'minor': 30, 'display': '30 JPY'}), ('normal control', {'price': 26, 'currency': 'KWD', 'num': 3, 'den': 31}, {'minor': 3, 'display': '0.003 KWD'}), ('normal control', {'price': -18, 'currency': 'JPY', 'num': 81, 'den': 365}, {'minor': -4, 'display': '-4 JPY'})], [('regression', {'price': -357324, 'currency': 'USD', 'num': 19, 'den': 30}, {'minor': -226305, 'display': '-2263.05 USD'}), ('regression (boundary)', {'price': -7, 'currency': 'KWD', 'num': 1, 'den': 2}, {'minor': -4, 'display': '-0.004 KWD'}), ('partial-repair probe', {'price': -927642, 'currency': 'KWD', 'num': 9, 'den': 31}, {'minor': -269315, 'display': '-269.315 KWD'}), ('partial-repair probe', {'price': -70708, 'currency': 'EUR', 'num': 787, 'den': 1000}, {'minor': -55647, 'display': '-556.47 EUR'}), ('boundary control', {'price': 5, 'currency': 'JPY', 'num': 1, 'den': 2}, {'minor': 3, 'display': '3 JPY'}), ('normal control', {'price': -48, 'currency': 'JPY', 'num': 0, 'den': 4}, {'minor': 0, 'display': '0 JPY'}), ('normal control', {'price': -79, 'currency': 'JPY', 'num': 200, 'den': 365}, {'minor': -43, 'display': '-43 JPY'}), ('normal control', {'price': -93, 'currency': 'EUR', 'num': 0, 'den': 2}, {'minor': 0, 'display': '0.00 EUR'}), ('normal control', {'price': 464209, 'currency': 'EUR', 'num': 10, 'den': 30}, {'minor': 154736, 'display': '1547.36 EUR'})], [('regression', {'price': -927642, 'currency': 'KWD', 'num': 9, 'den': 31}, {'minor': -269315, 'display': '-269.315 KWD'}), ('regression (boundary)', {'price': -105, 'currency': 'EUR', 'num': 1, 'den': 2}, {'minor': -53, 'display': '-0.53 EUR'}), ('partial-repair probe', {'price': -686147, 'currency': 'EUR', 'num': 2, 'den': 31}, {'minor': -44268, 'display': '-442.68 EUR'}), ('partial-repair probe', {'price': -272855, 'currency': 'KWD', 'num': 798, 'den': 1000}, {'minor': -217738, 'display': '-217.738 KWD'}), ('boundary control', {'price': 5, 'currency': 'JPY', 'num': 1, 'den': 2}, {'minor': 3, 'display': '3 JPY'}), ('normal control', {'price': 61, 'currency': 'JPY', 'num': 50, 'den': 365}, {'minor': 8, 'display': '8 JPY'}), ('normal control', {'price': 675691, 'currency': 'KWD', 'num': 214, 'den': 365}, {'minor': 396159, 'display': '396.159 KWD'}), ('normal control', {'price': 95, 'currency': 'USD', 'num': 25, 'den': 30}, {'minor': 79, 'display': '0.79 USD'}), ('normal control', {'price': 553663, 'currency': 'USD', 'num': 138, 'den': 365}, {'minor': 209330, 'display': '2093.30 USD'})], [('regression', {'price': -70708, 'currency': 'EUR', 'num': 787, 'den': 1000}, {'minor': -55647, 'display': '-556.47 EUR'}), ('regression', {'price': -6310, 'currency': 'EUR', 'num': 23, 'den': 31}, {'minor': -4682, 'display': '-46.82 EUR'}), ('partial-repair probe', {'price': -940440, 'currency': 'EUR', 'num': 894, 'den': 1000}, {'minor': -840753, 'display': '-8407.53 EUR'}), ('partial-repair probe', {'price': -345259, 'currency': 'EUR', 'num': 4, 'den': 4}, {'minor': -345259, 'display': '-3452.59 EUR'}), ('boundary control', {'price': 5, 'currency': 'JPY', 'num': 1, 'den': 2}, {'minor': 3, 'display': '3 JPY'}), ('normal control', {'price': 86, 'currency': 'EUR', 'num': 0, 'den': 2}, {'minor': 0, 'display': '0.00 EUR'}), ('normal control', {'price': 21, 'currency': 'JPY', 'num': 3, 'den': 30}, {'minor': 2, 'display': '2 JPY'}), ('normal control', {'price': 127, 'currency': 'JPY', 'num': 0, 'den': 2}, {'minor': 0, 'display': '0 JPY'}), ('normal control', {'price': 248141, 'currency': 'EUR', 'num': 187, 'den': 365}, {'minor': 127130, 'display': '1271.30 EUR'})], [('regression', {'price': -686147, 'currency': 'EUR', 'num': 2, 'den': 31}, {'minor': -44268, 'display': '-442.68 EUR'}), ('regression', {'price': -35, 'currency': 'KWD', 'num': 30, 'den': 30}, {'minor': -35, 'display': '-0.035 KWD'}), ('partial-repair probe', {'price': -799709, 'currency': 'USD', 'num': 177, 'den': 365}, {'minor': -387804, 'display': '-3878.04 USD'}), ('partial-repair probe', {'price': -45094, 'currency': 'EUR', 'num': 282, 'den': 365}, {'minor': -34840, 'display': '-348.40 EUR'}), ('boundary control', {'price': 5, 'currency': 'JPY', 'num': 1, 'den': 2}, {'minor': 3, 'display': '3 JPY'}), ('normal control', {'price': 8, 'currency': 'EUR', 'num': 25, 'den': 31}, {'minor': 6, 'display': '0.06 EUR'}), ('normal control', {'price': -19, 'currency': 'EUR', 'num': 0, 'den': 31}, {'minor': 0, 'display': '0.00 EUR'}), ('normal control', {'price': -70, 'currency': 'JPY', 'num': 209, 'den': 365}, {'minor': -40, 'display': '-40 JPY'}), ('normal control', {'price': 26512, 'currency': 'USD', 'num': 248, 'den': 365}, {'minor': 18014, 'display': '180.14 USD'})]]
for i, (label, args, expected) in enumerate(fixtures[N-1]):
    check("%s %d" % (label, i), 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 fixtureActualExpectedOutcome
regression 0{'display': '--46.82 EUR', 'minor': -4682}{'display': '-46.82 EUR', 'minor': -4682}Failed
regression (boundary) 1{'display': '-0.02 USD', 'minor': -2}{'display': '-0.02 USD', 'minor': -2}Passed
partial-repair probe 2{'display': '--2263.05 USD', 'minor': -226305}{'display': '-2263.05 USD', 'minor': -226305}Failed
partial-repair probe 3{'display': '--269.315 KWD', 'minor': -269315}{'display': '-269.315 KWD', 'minor': -269315}Failed
boundary control 4{'display': '3 JPY', 'minor': 3}{'display': '3 JPY', 'minor': 3}Passed
normal control 5{'display': '58 JPY', 'minor': 58}{'display': '58 JPY', 'minor': 58}Passed
normal control 6{'display': '30 JPY', 'minor': 30}{'display': '30 JPY', 'minor': 30}Passed
normal control 7{'display': '0.003 KWD', 'minor': 3}{'display': '0.003 KWD', 'minor': 3}Passed
normal control 8{'display': '-4 JPY', 'minor': -4}{'display': '-4 JPY', 'minor': -4}Passed

SHA-256 / d6b9257823ebfca731ecf94f6ff4c54975e5bfaf4ca2cfe244db348bdcbd0f7d

HELD IN THE MEMBER ARCHIVE

The verified repair and its recorded checks are member-only.

This mechanism has 9 recorded checks per implementation. The open-access tier publishes the failure and the unsuccessful fix; the repaired source that passes every check, and the observations that prove it, are available to members.

Every case sharing this mechanism uses the same contract and the same repair, so this one record is held back for all of them.

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Verification & scope

A deterministic teaching model of a stipulated billing rule. It makes no claim to reproduce any billing provider's exact behaviour and is not billing software. 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 2026-09-29T14:46:37.084090+00:00.

Case digest / 65f1b1cd6905140056f363feab3750b84f6fec4a9be824e9ced044d764aca5a6