FA-62156 / Currency rounding and FX conversion / Open access

The minor-unit fraction is not zero-padded on the left · case 01

105 cents renders as '$1.5'.

Verified by executionVariant 1 · 6 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

str(frac) is appended without left zero padding.

VERIFIED REPAIR

Left-pad the fraction with zeros to the exponent width.

Unsuccessful approach: Right-padding turns 1.05 into '1.50'.

Case contract

solve(minor, ccy): format integer minor units. Styles: USD '$' prefix, ',' groups, '.' decimal, 2 digits; EUR ' €' suffix, '.' groups, ',' decimal, 2; JPY '¥' prefix, ',' groups, 0 digits (no decimal separator); CHF 'CHF ' prefix, "'" groups, '.', 2; KWD 'KD ' prefix, ',', '.', 3. Group the whole part in threes from the right; the fraction is zero-padded to the exponent. A negative amount places '-' before everything. Unknown codes return 'ERR:currency'.

Why this case matters

Currency amounts must be rounded at the right stage and in the right unit, or ledgers, quotes and settlements drift by minor units.

1 / The failure

Exit 1

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

N = 1
observations = []
def solve(minor, ccy):
    spec = {'USD': ('$', '', ',', '.', 2), 'EUR': ('', ' €', '.', ',', 2), 'JPY': ('¥', '', ',', '.', 0), 'CHF': ('CHF ', '', "'", '.', 2), 'KWD': ('KD ', '', ',', '.', 3)}
    if ccy not in spec: return 'ERR:currency'
    pre, suf, grp, dec, e = spec[ccy]
    neg = minor < 0
    major, frac = divmod(abs(minor), 10 ** e)
    digits = str(major)
    groups = []
    while len(digits) > 3:
        groups.insert(0, digits[-3:])
        digits = digits[:-3]
    groups.insert(0, digits)
    body = grp.join(groups)
    if e: body += dec + str(frac)
    return ('-' if neg else '') + pre + body + suf
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
cases = [[('regression fraction-zero-fill 1', (105, 'USD'), '$1.05'),
  ('regression fraction-zero-fill 2', (1005, 'KWD'), 'KD 1.005'), ('control: dollars', (123450, 'USD'), '$1,234.50'),
  ('control: negative dollars', (-150, 'USD'), '-$1.50'), ('control: negative euro cents', (-50, 'EUR'), '-0,50 €'),
  ('control: yen', (1234567, 'JPY'), '¥1,234,567')],
 [('regression fraction-zero-fill 1', (100000000, 'EUR'), '1.000.000,00 €'),
  ('regression fraction-zero-fill 2', (-1000000, 'EUR'), '-10.000,00 €'),
  ('partial repair guard 1', (-50, 'KWD'), '-KD 0.050'), ('partial repair guard 2', (5, 'CHF'), 'CHF 0.05'),
  ('control: yen', (1234567, 'JPY'), '¥1,234,567'), ('control: franc', (12345678, 'CHF'), "CHF 123'456.78"),
  ('control: dinar', (1005, 'KWD'), 'KD 1.005'), ('control: unknown', (5, 'GBP'), 'ERR:currency')],
 [('regression fraction-zero-fill 1', (0, 'CHF'), 'CHF 0.00'),
  ('regression fraction-zero-fill 2', (-100000, 'USD'), '-$1,000.00'),
  ('partial repair guard 1', (105, 'EUR'), '1,05 €'), ('partial repair guard 2', (5, 'EUR'), '0,05 €'),
  ('control: unknown', (5, 'GBP'), 'ERR:currency'), ('control: million euros', (100000000, 'EUR'), '1.000.000,00 €'),
  ('control: zero yen', (0, 'JPY'), '¥0'), ('control: small dollars', (105, 'USD'), '$1.05')],
 [('regression fraction-zero-fill 1', (-50, 'KWD'), '-KD 0.050'),
  ('regression fraction-zero-fill 2', (5, 'CHF'), 'CHF 0.05'), ('partial repair guard 1', (-105, 'EUR'), '-1,05 €'),
  ('partial repair guard 2', (-5, 'CHF'), '-CHF 0.05'), ('control: small dollars', (105, 'USD'), '$1.05'),
  ('control: negative yen', (-1000, 'JPY'), '-¥1,000'), ('control: dollars', (123450, 'USD'), '$1,234.50'),
  ('control: negative dollars', (-150, 'USD'), '-$1.50')],
 [('regression fraction-zero-fill 1', (1000, 'USD'), '$10.00'),
  ('regression fraction-zero-fill 2', (105, 'EUR'), '1,05 €'), ('partial repair guard 1', (-5, 'USD'), '-$0.05'),
  ('partial repair guard 2', (50, 'KWD'), 'KD 0.050'), ('control: negative dollars', (-150, 'USD'), '-$1.50'),
  ('control: negative euro cents', (-50, 'EUR'), '-0,50 €'), ('control: yen', (1234567, 'JPY'), '¥1,234,567'),
  ('control: franc', (12345678, 'CHF'), "CHF 123'456.78")]]
for label, args, expected in cases[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 fraction-zero-fill 1	`$1.5`	`$1.05`	Failed
regression fraction-zero-fill 2	`KD 1.5`	`KD 1.005`	Failed
control: dollars	`$1,234.50`	`$1,234.50`	Passed
control: negative dollars	`-$1.50`	`-$1.50`	Passed
control: negative euro cents	`-0,50 €`	`-0,50 €`	Passed
control: yen	`¥1,234,567`	`¥1,234,567`	Passed

SHA-256 / dc646f39c02f6f1348942d153ae45b5307d36875dce6125ba42c289f3555ea2e

2 / The unsuccessful fix

Exit 1

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

N = 1
observations = []
def solve(minor, ccy):
    spec = {'USD': ('$', '', ',', '.', 2), 'EUR': ('', ' €', '.', ',', 2), 'JPY': ('¥', '', ',', '.', 0), 'CHF': ('CHF ', '', "'", '.', 2), 'KWD': ('KD ', '', ',', '.', 3)}
    if ccy not in spec: return 'ERR:currency'
    pre, suf, grp, dec, e = spec[ccy]
    neg = minor < 0
    major, frac = divmod(abs(minor), 10 ** e)
    digits = str(major)
    groups = []
    while len(digits) > 3:
        groups.insert(0, digits[-3:])
        digits = digits[:-3]
    groups.insert(0, digits)
    body = grp.join(groups)
    if e: body += dec + str(frac).ljust(e, '0')
    return ('-' if neg else '') + pre + body + suf
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
cases = [[('regression fraction-zero-fill 1', (105, 'USD'), '$1.05'),
  ('regression fraction-zero-fill 2', (1005, 'KWD'), 'KD 1.005'), ('control: dollars', (123450, 'USD'), '$1,234.50'),
  ('control: negative dollars', (-150, 'USD'), '-$1.50'), ('control: negative euro cents', (-50, 'EUR'), '-0,50 €'),
  ('control: yen', (1234567, 'JPY'), '¥1,234,567')],
 [('regression fraction-zero-fill 1', (100000000, 'EUR'), '1.000.000,00 €'),
  ('regression fraction-zero-fill 2', (-1000000, 'EUR'), '-10.000,00 €'),
  ('partial repair guard 1', (-50, 'KWD'), '-KD 0.050'), ('partial repair guard 2', (5, 'CHF'), 'CHF 0.05'),
  ('control: yen', (1234567, 'JPY'), '¥1,234,567'), ('control: franc', (12345678, 'CHF'), "CHF 123'456.78"),
  ('control: dinar', (1005, 'KWD'), 'KD 1.005'), ('control: unknown', (5, 'GBP'), 'ERR:currency')],
 [('regression fraction-zero-fill 1', (0, 'CHF'), 'CHF 0.00'),
  ('regression fraction-zero-fill 2', (-100000, 'USD'), '-$1,000.00'),
  ('partial repair guard 1', (105, 'EUR'), '1,05 €'), ('partial repair guard 2', (5, 'EUR'), '0,05 €'),
  ('control: unknown', (5, 'GBP'), 'ERR:currency'), ('control: million euros', (100000000, 'EUR'), '1.000.000,00 €'),
  ('control: zero yen', (0, 'JPY'), '¥0'), ('control: small dollars', (105, 'USD'), '$1.05')],
 [('regression fraction-zero-fill 1', (-50, 'KWD'), '-KD 0.050'),
  ('regression fraction-zero-fill 2', (5, 'CHF'), 'CHF 0.05'), ('partial repair guard 1', (-105, 'EUR'), '-1,05 €'),
  ('partial repair guard 2', (-5, 'CHF'), '-CHF 0.05'), ('control: small dollars', (105, 'USD'), '$1.05'),
  ('control: negative yen', (-1000, 'JPY'), '-¥1,000'), ('control: dollars', (123450, 'USD'), '$1,234.50'),
  ('control: negative dollars', (-150, 'USD'), '-$1.50')],
 [('regression fraction-zero-fill 1', (1000, 'USD'), '$10.00'),
  ('regression fraction-zero-fill 2', (105, 'EUR'), '1,05 €'), ('partial repair guard 1', (-5, 'USD'), '-$0.05'),
  ('partial repair guard 2', (50, 'KWD'), 'KD 0.050'), ('control: negative dollars', (-150, 'USD'), '-$1.50'),
  ('control: negative euro cents', (-50, 'EUR'), '-0,50 €'), ('control: yen', (1234567, 'JPY'), '¥1,234,567'),
  ('control: franc', (12345678, 'CHF'), "CHF 123'456.78")]]
for label, args, expected in cases[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 fraction-zero-fill 1	`$1.50`	`$1.05`	Failed
regression fraction-zero-fill 2	`KD 1.500`	`KD 1.005`	Failed
control: dollars	`$1,234.50`	`$1,234.50`	Passed
control: negative dollars	`-$1.50`	`-$1.50`	Passed
control: negative euro cents	`-0,50 €`	`-0,50 €`	Passed
control: yen	`¥1,234,567`	`¥1,234,567`	Passed

SHA-256 / 47070ba18ffa382955698d43f08e044a654f2169fbdab6b929182de91537d9a5

3 / The verified repair

Exit 0

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

N = 1
observations = []
def solve(minor, ccy):
    spec = {'USD': ('$', '', ',', '.', 2), 'EUR': ('', ' €', '.', ',', 2), 'JPY': ('¥', '', ',', '.', 0), 'CHF': ('CHF ', '', "'", '.', 2), 'KWD': ('KD ', '', ',', '.', 3)}
    if ccy not in spec: return 'ERR:currency'
    pre, suf, grp, dec, e = spec[ccy]
    neg = minor < 0
    major, frac = divmod(abs(minor), 10 ** e)
    digits = str(major)
    groups = []
    while len(digits) > 3:
        groups.insert(0, digits[-3:])
        digits = digits[:-3]
    groups.insert(0, digits)
    body = grp.join(groups)
    if e: body += dec + str(frac).zfill(e)
    return ('-' if neg else '') + pre + body + suf
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
cases = [[('regression fraction-zero-fill 1', (105, 'USD'), '$1.05'),
  ('regression fraction-zero-fill 2', (1005, 'KWD'), 'KD 1.005'), ('control: dollars', (123450, 'USD'), '$1,234.50'),
  ('control: negative dollars', (-150, 'USD'), '-$1.50'), ('control: negative euro cents', (-50, 'EUR'), '-0,50 €'),
  ('control: yen', (1234567, 'JPY'), '¥1,234,567')],
 [('regression fraction-zero-fill 1', (100000000, 'EUR'), '1.000.000,00 €'),
  ('regression fraction-zero-fill 2', (-1000000, 'EUR'), '-10.000,00 €'),
  ('partial repair guard 1', (-50, 'KWD'), '-KD 0.050'), ('partial repair guard 2', (5, 'CHF'), 'CHF 0.05'),
  ('control: yen', (1234567, 'JPY'), '¥1,234,567'), ('control: franc', (12345678, 'CHF'), "CHF 123'456.78"),
  ('control: dinar', (1005, 'KWD'), 'KD 1.005'), ('control: unknown', (5, 'GBP'), 'ERR:currency')],
 [('regression fraction-zero-fill 1', (0, 'CHF'), 'CHF 0.00'),
  ('regression fraction-zero-fill 2', (-100000, 'USD'), '-$1,000.00'),
  ('partial repair guard 1', (105, 'EUR'), '1,05 €'), ('partial repair guard 2', (5, 'EUR'), '0,05 €'),
  ('control: unknown', (5, 'GBP'), 'ERR:currency'), ('control: million euros', (100000000, 'EUR'), '1.000.000,00 €'),
  ('control: zero yen', (0, 'JPY'), '¥0'), ('control: small dollars', (105, 'USD'), '$1.05')],
 [('regression fraction-zero-fill 1', (-50, 'KWD'), '-KD 0.050'),
  ('regression fraction-zero-fill 2', (5, 'CHF'), 'CHF 0.05'), ('partial repair guard 1', (-105, 'EUR'), '-1,05 €'),
  ('partial repair guard 2', (-5, 'CHF'), '-CHF 0.05'), ('control: small dollars', (105, 'USD'), '$1.05'),
  ('control: negative yen', (-1000, 'JPY'), '-¥1,000'), ('control: dollars', (123450, 'USD'), '$1,234.50'),
  ('control: negative dollars', (-150, 'USD'), '-$1.50')],
 [('regression fraction-zero-fill 1', (1000, 'USD'), '$10.00'),
  ('regression fraction-zero-fill 2', (105, 'EUR'), '1,05 €'), ('partial repair guard 1', (-5, 'USD'), '-$0.05'),
  ('partial repair guard 2', (50, 'KWD'), 'KD 0.050'), ('control: negative dollars', (-150, 'USD'), '-$1.50'),
  ('control: negative euro cents', (-50, 'EUR'), '-0,50 €'), ('control: yen', (1234567, 'JPY'), '¥1,234,567'),
  ('control: franc', (12345678, 'CHF'), "CHF 123'456.78")]]
for label, args, expected in cases[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 fraction-zero-fill 1	`$1.05`	`$1.05`	Passed
regression fraction-zero-fill 2	`KD 1.005`	`KD 1.005`	Passed
control: dollars	`$1,234.50`	`$1,234.50`	Passed
control: negative dollars	`-$1.50`	`-$1.50`	Passed
control: negative euro cents	`-0,50 €`	`-0,50 €`	Passed
control: yen	`¥1,234,567`	`¥1,234,567`	Passed

SHA-256 / 8021f0fb61c01f3410fb903919064c41aff3c62ffa95e9f2800d1ee460c53e41

Verification & scope

A deterministic, bounded teaching model with a stipulated toy contract; it makes no claim of conformance to any real regulation, standard, or institution's rules. 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 2026-09-29T14:47:02.020763+00:00.

Case digest / cdb53fdea9689b7151d5cd144146b35894de0d0e9cd04d76df16d8fcf8bc6c07