FA-61876 / Currency rounding and FX conversion / Open access

The converted amount is rounded with the source currency exponent · case 01

Euro converted to yen is printed with two decimals, and yen converted to dinar loses decimals.

Verified by executionVariant 1 · 7 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

The quantum is taken from exps[frm] instead of exps[to].

VERIFIED REPAIR

Round at the target currency's exponent.

Unsuccessful approach: Using the larger of the two exponents still prints fractional yen when the source has cents.

Case contract

solve(amount, frm, to, rates): rates maps a currency to units of that currency per 1 USD (decimal strings); USD is implicitly 1 when absent. Convert exactly as amount / rate[frm] * rate[to] with no intermediate rounding, then round half-even to the target exponent (USD/EUR/GBP/CHF/SEK/NOK 2, JPY/KRW 0, KWD 3, CLF 4) and return a plain string. A missing rate returns 'ERR:no-rate:<code>', a zero or negative rate 'ERR:bad-rate:<code>' (source checked first).

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
from decimal import Decimal, ROUND_HALF_EVEN, ROUND_HALF_UP, ROUND_FLOOR, ROUND_CEILING, ROUND_DOWN, ROUND_UP, ROUND_HALF_DOWN
N = 1
observations = []
def solve(amount, frm, to, rates):
    exps = {'USD': 2, 'EUR': 2, 'GBP': 2, 'CHF': 2, 'SEK': 2, 'NOK': 2, 'JPY': 0, 'KRW': 0, 'KWD': 3, 'CLF': 4}
    def rate(c):
        if c == 'USD' and c not in rates: return Decimal(1)
        if c not in rates: return None
        return Decimal(rates[c])
    rf, rt = rate(frm), rate(to)
    for c, r in ((frm, rf), (to, rt)):
        if r is None: return 'ERR:no-rate:' + c
        if r <= 0: return 'ERR:bad-rate:' + c
    usd = Decimal(amount) / rf
    out = usd * rt
    return format(out.quantize(Decimal(1).scaleb(-exps[frm]), rounding=ROUND_HALF_EVEN), 'f')
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
cases = [[('regression target-exponent 1',
   ('100', 'EUR', 'JPY',
    {'EUR': '0.92',
     'JPY': '151.37',
     'KRW': '1352.5',
     'KWD': '0.3071',
     'GBP': '0.7893',
     'CLF': '0.02451',
     'CHF': '0.8801'}),
   '16453'),
  ('regression target-exponent 2',
   ('100.00', 'USD', 'KWD',
    {'EUR': '0.92',
     'JPY': '151.37',
     'KRW': '1352.5',
     'KWD': '0.3071',
     'GBP': '0.7893',
     'CLF': '0.02451',
     'CHF': '0.8801'}),
   '30.710'),
  ('partial repair guard 2',
   ('19481.34', 'KWD', 'USD',
    {'EUR': '0.92',
     'JPY': '151.37',
     'KRW': '1352.5',
     'KWD': '0.3071',
     'GBP': '0.7893',
     'CLF': '0.02451',
     'CHF': '0.8801'}),
   '63436.47'),
  ('control: pound to usd',
   ('5', 'GBP', 'USD',
    {'EUR': '0.92',
     'JPY': '151.37',
     'KRW': '1352.5',
     'KWD': '0.3071',
     'GBP': '0.7893',
     'CLF': '0.02451',
     'CHF': '0.8801'}),
   '6.33'),
  ('control: missing target',
   ('1', 'EUR', 'SEK',
    {'EUR': '0.92',
     'JPY': '151.37',
     'KRW': '1352.5',
     'KWD': '0.3071',
     'GBP': '0.7893',
     'CLF': '0.02451',
     'CHF': '0.8801'}),
   'ERR:no-rate:SEK'),
  ('control: won to franc',
   ('250000', 'KRW', 'CHF',
    {'EUR': '0.92',
     'JPY': '151.37',
     'KRW': '1352.5',
     'KWD': '0.3071',
     'GBP': '0.7893',
     'CLF': '0.02451',
     'CHF': '0.8801'}),
   '162.68'),
  ('control: yen to unit of account',
   ('99999', 'JPY', 'CLF',
    {'EUR': '0.92',
     'JPY': '151.37',
     'KRW': '1352.5',
     'KWD': '0.3071',
     'GBP': '0.7893',
     'CLF': '0.02451',
     'CHF': '0.8801'}),
   '16.1920')],
 [('regression target-exponent 1',
   ('250000', 'KRW', 'CHF',
    {'EUR': '0.92',
     'JPY': '151.37',
     'KRW': '1352.5',
     'KWD': '0.3071',
     'GBP': '0.7893',
     'CLF': '0.02451',
     'CHF': '0.8801'}),
   '162.68'),
  ('regression target-exponent 2',
   ('99999', 'JPY', 'CLF',
    {'EUR': '0.92',
     'JPY': '151.37',
     'KRW': '1352.5',
     'KWD': '0.3071',
     'GBP': '0.7893',
     'CLF': '0.02451',
     'CHF': '0.8801'}),
   '16.1920'),
  ('partial repair guard 1',
   ('31699.892', 'KWD', 'USD',
    {'EUR': '0.92', 'KRW': '1352.5', 'KWD': '0.3071', 'GBP': '0.7893', 'CLF': '0.02451', 'CHF': '0.8801'}),
   '103223.35'),
  ('partial repair guard 2',
   ('2442.484', 'CHF', 'JPY',
    {'EUR': '0.92', 'JPY': '151.37', 'KWD': '0.3071', 'GBP': '0.7893', 'CLF': '0.02451', 'CHF': '0.8801', 'USD': '1'}),
   '420087'),
  ('control: missing target',
   ('1', 'EUR', 'SEK',
    {'EUR': '0.92',
     'JPY': '151.37',
     'KRW': '1352.5',
     'KWD': '0.3071',
     'GBP': '0.7893',
     'CLF': '0.02451',
     'CHF': '0.8801'}),
   'ERR:no-rate:SEK'),
  ('control: zero rate target', ('10', 'EUR', 'CHF', {'EUR': '0.92', 'CHF': '0'}), 'ERR:bad-rate:CHF'),
  ('control: explicit usd rate', ('10', 'USD', 'EUR', {'USD': '1', 'EUR': '0.92'}), '9.20'),
  ('control: usd absent', ('42.42', 'EUR', 'USD', {'EUR': '0.92'}), '46.11')],
 [('regression target-exponent 1',
   ('113222', 'EUR', 'CLF',
    {'EUR': '0.92', 'JPY': '151.37', 'KWD': '0.3071', 'GBP': '0.7893', 'CLF': '0.02451', 'CHF': '0.8801'}),
   '3016.3818'),
  ('regression target-exponent 2',
   ('19481.34', 'KWD', 'USD',
    {'EUR': '0.92',
     'JPY': '151.37',
     'KRW': '1352.5',
     'KWD': '0.3071',
     'GBP': '0.7893',
     'CLF': '0.02451',
     'CHF': '0.8801'}),
   '63436.47'),
  ('partial repair guard 1',
   ('132236.08', 'CLF', 'KRW', {'EUR': '0.92', 'JPY': '151.37', 'KRW': '1352.5', 'CLF': '0.02451', 'CHF': '0.8801'}),
   '7296992991'),
  ('partial repair guard 2',
   ('23223.04', 'CLF', 'KWD',
    {'EUR': '0.92', 'KRW': '1352.5', 'KWD': '0.3071', 'GBP': '0.7893', 'CLF': '0.02451', 'CHF': '0.8801'}),
   '290974.932'),
  ('control: zero rate target', ('10', 'EUR', 'CHF', {'EUR': '0.92', 'CHF': '0'}), 'ERR:bad-rate:CHF'),
  ('control: explicit usd rate', ('10', 'USD', 'EUR', {'USD': '1', 'EUR': '0.92'}), '9.20'),
  ('control: usd absent', ('42.42', 'EUR', 'USD', {'EUR': '0.92'}), '46.11'),
  ('control: euro to yen',
   ('100', 'EUR', 'JPY',
    {'EUR': '0.92',
     'JPY': '151.37',
     'KRW': '1352.5',
     'KWD': '0.3071',
     'GBP': '0.7893',
     'CLF': '0.02451',
     'CHF': '0.8801'}),
   '16453')],
 [('regression target-exponent 1',
   ('12406.83', 'JPY', 'USD',
    {'EUR': '0.92',
     'JPY': '151.37',
     'KRW': '1352.5',
     'KWD': '0.3071',
     'GBP': '0.7893',
     'CLF': '0.02451',
     'CHF': '0.8801',
     'USD': '1'}),
   '81.96'),
  ('regression target-exponent 2',
   ('69492.535', 'JPY', 'EUR',
    {'EUR': '0.92',
     'JPY': '151.37',
     'KRW': '0',
     'KWD': '0.3071',
     'GBP': '0.7893',
     'CLF': '0.02451',
     'CHF': '0.8801',
     'USD': '1'}),
   '422.36'),
  ('partial repair guard 1',
   ('62580.312', 'CHF', 'KRW',
    {'EUR': '0.92', 'JPY': '151.37', 'KRW': '1352.5', 'KWD': '0.3071', 'GBP': '0.7893', 'CHF': '0.8801'}),
   '96170744'),
  ('partial repair guard 2',
   ('86444.328', 'KWD', 'KRW',
    {'EUR': '0.92', 'JPY': '151.37', 'KRW': '1352.5', 'KWD': '0.3071', 'GBP': '0.7893', 'CLF': '0.02451'}),
   '380709715'),
  ('control: euro to yen',
   ('100', 'EUR', 'JPY',
    {'EUR': '0.92',
     'JPY': '151.37',
     'KRW': '1352.5',
     'KWD': '0.3071',
     'GBP': '0.7893',
     'CLF': '0.02451',
     'CHF': '0.8801'}),
   '16453'),
  ('control: usd to dinar',
   ('100.00', 'USD', 'KWD',
    {'EUR': '0.92',
     'JPY': '151.37',
     'KRW': '1352.5',
     'KWD': '0.3071',
     'GBP': '0.7893',
     'CLF': '0.02451',
     'CHF': '0.8801'}),
   '30.710'),
  ('control: pound to usd',
   ('5', 'GBP', 'USD',
    {'EUR': '0.92',
     'JPY': '151.37',
     'KRW': '1352.5',
     'KWD': '0.3071',
     'GBP': '0.7893',
     'CLF': '0.02451',
     'CHF': '0.8801'}),
   '6.33'),
  ('control: missing target',
   ('1', 'EUR', 'SEK',
    {'EUR': '0.92',
     'JPY': '151.37',
     'KRW': '1352.5',
     'KWD': '0.3071',
     'GBP': '0.7893',
     'CLF': '0.02451',
     'CHF': '0.8801'}),
   'ERR:no-rate:SEK')],
 [('regression target-exponent 1',
   ('31699.892', 'KWD', 'USD',
    {'EUR': '0.92', 'KRW': '1352.5', 'KWD': '0.3071', 'GBP': '0.7893', 'CLF': '0.02451', 'CHF': '0.8801'}),
   '103223.35'),
  ('regression target-exponent 2',
   ('48429.445', 'EUR', 'KWD',
    {'EUR': '0.92',
     'JPY': '151.37',
     'KRW': '1352.5',
     'KWD': '0.3071',
     'GBP': '0.7893',
     'CLF': '0.02451',
     'CHF': '0.8801'}),
   '16165.959'),
  ('partial repair guard 1',
   ('31654.45', 'KWD', 'CHF',
    {'EUR': '0.92',
     'JPY': '151.37',
     'KRW': '1352.5',
     'KWD': '0.3071',
     'GBP': '-1.2',
     'CLF': '0.02451',
     'CHF': '0.8801',
     'USD': '1'}),
   '90716.64'),
  ('partial repair guard 2',
   ('45677.89', 'GBP', 'KRW',
    {'EUR': '0.92',
     'JPY': '151.37',
     'KRW': '1352.5',
     'KWD': '0.3071',
     'GBP': '0.7893',
     'CLF': '0.02451',
     'CHF': '0.8801',
     'USD': '1'}),
   '78271058'),
  ('control: missing target',
   ('1', 'EUR', 'SEK',
    {'EUR': '0.92',
     'JPY': '151.37',
     'KRW': '1352.5',
     'KWD': '0.3071',
     'GBP': '0.7893',
     'CLF': '0.02451',
     'CHF': '0.8801'}),
   'ERR:no-rate:SEK'),
  ('control: won to franc',
   ('250000', 'KRW', 'CHF',
    {'EUR': '0.92',
     'JPY': '151.37',
     'KRW': '1352.5',
     'KWD': '0.3071',
     'GBP': '0.7893',
     'CLF': '0.02451',
     'CHF': '0.8801'}),
   '162.68'),
  ('control: yen to unit of account',
   ('99999', 'JPY', 'CLF',
    {'EUR': '0.92',
     'JPY': '151.37',
     'KRW': '1352.5',
     'KWD': '0.3071',
     'GBP': '0.7893',
     'CLF': '0.02451',
     'CHF': '0.8801'}),
   '16.1920'),
  ('control: zero rate target', ('10', 'EUR', 'CHF', {'EUR': '0.92', 'CHF': '0'}), 'ERR:bad-rate:CHF')]]
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 target-exponent 1	`16453.26`	`16453`	Failed
regression target-exponent 2	`30.71`	`30.710`	Failed
partial repair guard 2	`63436.470`	`63436.47`	Failed
control: pound to usd	`6.33`	`6.33`	Passed
control: missing target	`ERR:no-rate:SEK`	`ERR:no-rate:SEK`	Passed
control: won to franc	`163`	`162.68`	Failed
control: yen to unit of account	`16`	`16.1920`	Failed

SHA-256 / 19bf258c9c1bda83f5c401b9f5994a1cba2ba1da931c7f8ac8cf2af6f0bdc8f8

2 / The unsuccessful fix

Exit 1

"""Failure Map reference implementation. Python standard library only."""
import json
from decimal import Decimal, ROUND_HALF_EVEN, ROUND_HALF_UP, ROUND_FLOOR, ROUND_CEILING, ROUND_DOWN, ROUND_UP, ROUND_HALF_DOWN
N = 1
observations = []
def solve(amount, frm, to, rates):
    exps = {'USD': 2, 'EUR': 2, 'GBP': 2, 'CHF': 2, 'SEK': 2, 'NOK': 2, 'JPY': 0, 'KRW': 0, 'KWD': 3, 'CLF': 4}
    def rate(c):
        if c == 'USD' and c not in rates: return Decimal(1)
        if c not in rates: return None
        return Decimal(rates[c])
    rf, rt = rate(frm), rate(to)
    for c, r in ((frm, rf), (to, rt)):
        if r is None: return 'ERR:no-rate:' + c
        if r <= 0: return 'ERR:bad-rate:' + c
    usd = Decimal(amount) / rf
    out = usd * rt
    return format(out.quantize(Decimal(1).scaleb(-max(exps[frm], exps[to])), rounding=ROUND_HALF_EVEN), 'f')
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
cases = [[('regression target-exponent 1',
   ('100', 'EUR', 'JPY',
    {'EUR': '0.92',
     'JPY': '151.37',
     'KRW': '1352.5',
     'KWD': '0.3071',
     'GBP': '0.7893',
     'CLF': '0.02451',
     'CHF': '0.8801'}),
   '16453'),
  ('regression target-exponent 2',
   ('100.00', 'USD', 'KWD',
    {'EUR': '0.92',
     'JPY': '151.37',
     'KRW': '1352.5',
     'KWD': '0.3071',
     'GBP': '0.7893',
     'CLF': '0.02451',
     'CHF': '0.8801'}),
   '30.710'),
  ('partial repair guard 2',
   ('19481.34', 'KWD', 'USD',
    {'EUR': '0.92',
     'JPY': '151.37',
     'KRW': '1352.5',
     'KWD': '0.3071',
     'GBP': '0.7893',
     'CLF': '0.02451',
     'CHF': '0.8801'}),
   '63436.47'),
  ('control: pound to usd',
   ('5', 'GBP', 'USD',
    {'EUR': '0.92',
     'JPY': '151.37',
     'KRW': '1352.5',
     'KWD': '0.3071',
     'GBP': '0.7893',
     'CLF': '0.02451',
     'CHF': '0.8801'}),
   '6.33'),
  ('control: missing target',
   ('1', 'EUR', 'SEK',
    {'EUR': '0.92',
     'JPY': '151.37',
     'KRW': '1352.5',
     'KWD': '0.3071',
     'GBP': '0.7893',
     'CLF': '0.02451',
     'CHF': '0.8801'}),
   'ERR:no-rate:SEK'),
  ('control: won to franc',
   ('250000', 'KRW', 'CHF',
    {'EUR': '0.92',
     'JPY': '151.37',
     'KRW': '1352.5',
     'KWD': '0.3071',
     'GBP': '0.7893',
     'CLF': '0.02451',
     'CHF': '0.8801'}),
   '162.68'),
  ('control: yen to unit of account',
   ('99999', 'JPY', 'CLF',
    {'EUR': '0.92',
     'JPY': '151.37',
     'KRW': '1352.5',
     'KWD': '0.3071',
     'GBP': '0.7893',
     'CLF': '0.02451',
     'CHF': '0.8801'}),
   '16.1920')],
 [('regression target-exponent 1',
   ('250000', 'KRW', 'CHF',
    {'EUR': '0.92',
     'JPY': '151.37',
     'KRW': '1352.5',
     'KWD': '0.3071',
     'GBP': '0.7893',
     'CLF': '0.02451',
     'CHF': '0.8801'}),
   '162.68'),
  ('regression target-exponent 2',
   ('99999', 'JPY', 'CLF',
    {'EUR': '0.92',
     'JPY': '151.37',
     'KRW': '1352.5',
     'KWD': '0.3071',
     'GBP': '0.7893',
     'CLF': '0.02451',
     'CHF': '0.8801'}),
   '16.1920'),
  ('partial repair guard 1',
   ('31699.892', 'KWD', 'USD',
    {'EUR': '0.92', 'KRW': '1352.5', 'KWD': '0.3071', 'GBP': '0.7893', 'CLF': '0.02451', 'CHF': '0.8801'}),
   '103223.35'),
  ('partial repair guard 2',
   ('2442.484', 'CHF', 'JPY',
    {'EUR': '0.92', 'JPY': '151.37', 'KWD': '0.3071', 'GBP': '0.7893', 'CLF': '0.02451', 'CHF': '0.8801', 'USD': '1'}),
   '420087'),
  ('control: missing target',
   ('1', 'EUR', 'SEK',
    {'EUR': '0.92',
     'JPY': '151.37',
     'KRW': '1352.5',
     'KWD': '0.3071',
     'GBP': '0.7893',
     'CLF': '0.02451',
     'CHF': '0.8801'}),
   'ERR:no-rate:SEK'),
  ('control: zero rate target', ('10', 'EUR', 'CHF', {'EUR': '0.92', 'CHF': '0'}), 'ERR:bad-rate:CHF'),
  ('control: explicit usd rate', ('10', 'USD', 'EUR', {'USD': '1', 'EUR': '0.92'}), '9.20'),
  ('control: usd absent', ('42.42', 'EUR', 'USD', {'EUR': '0.92'}), '46.11')],
 [('regression target-exponent 1',
   ('113222', 'EUR', 'CLF',
    {'EUR': '0.92', 'JPY': '151.37', 'KWD': '0.3071', 'GBP': '0.7893', 'CLF': '0.02451', 'CHF': '0.8801'}),
   '3016.3818'),
  ('regression target-exponent 2',
   ('19481.34', 'KWD', 'USD',
    {'EUR': '0.92',
     'JPY': '151.37',
     'KRW': '1352.5',
     'KWD': '0.3071',
     'GBP': '0.7893',
     'CLF': '0.02451',
     'CHF': '0.8801'}),
   '63436.47'),
  ('partial repair guard 1',
   ('132236.08', 'CLF', 'KRW', {'EUR': '0.92', 'JPY': '151.37', 'KRW': '1352.5', 'CLF': '0.02451', 'CHF': '0.8801'}),
   '7296992991'),
  ('partial repair guard 2',
   ('23223.04', 'CLF', 'KWD',
    {'EUR': '0.92', 'KRW': '1352.5', 'KWD': '0.3071', 'GBP': '0.7893', 'CLF': '0.02451', 'CHF': '0.8801'}),
   '290974.932'),
  ('control: zero rate target', ('10', 'EUR', 'CHF', {'EUR': '0.92', 'CHF': '0'}), 'ERR:bad-rate:CHF'),
  ('control: explicit usd rate', ('10', 'USD', 'EUR', {'USD': '1', 'EUR': '0.92'}), '9.20'),
  ('control: usd absent', ('42.42', 'EUR', 'USD', {'EUR': '0.92'}), '46.11'),
  ('control: euro to yen',
   ('100', 'EUR', 'JPY',
    {'EUR': '0.92',
     'JPY': '151.37',
     'KRW': '1352.5',
     'KWD': '0.3071',
     'GBP': '0.7893',
     'CLF': '0.02451',
     'CHF': '0.8801'}),
   '16453')],
 [('regression target-exponent 1',
   ('12406.83', 'JPY', 'USD',
    {'EUR': '0.92',
     'JPY': '151.37',
     'KRW': '1352.5',
     'KWD': '0.3071',
     'GBP': '0.7893',
     'CLF': '0.02451',
     'CHF': '0.8801',
     'USD': '1'}),
   '81.96'),
  ('regression target-exponent 2',
   ('69492.535', 'JPY', 'EUR',
    {'EUR': '0.92',
     'JPY': '151.37',
     'KRW': '0',
     'KWD': '0.3071',
     'GBP': '0.7893',
     'CLF': '0.02451',
     'CHF': '0.8801',
     'USD': '1'}),
   '422.36'),
  ('partial repair guard 1',
   ('62580.312', 'CHF', 'KRW',
    {'EUR': '0.92', 'JPY': '151.37', 'KRW': '1352.5', 'KWD': '0.3071', 'GBP': '0.7893', 'CHF': '0.8801'}),
   '96170744'),
  ('partial repair guard 2',
   ('86444.328', 'KWD', 'KRW',
    {'EUR': '0.92', 'JPY': '151.37', 'KRW': '1352.5', 'KWD': '0.3071', 'GBP': '0.7893', 'CLF': '0.02451'}),
   '380709715'),
  ('control: euro to yen',
   ('100', 'EUR', 'JPY',
    {'EUR': '0.92',
     'JPY': '151.37',
     'KRW': '1352.5',
     'KWD': '0.3071',
     'GBP': '0.7893',
     'CLF': '0.02451',
     'CHF': '0.8801'}),
   '16453'),
  ('control: usd to dinar',
   ('100.00', 'USD', 'KWD',
    {'EUR': '0.92',
     'JPY': '151.37',
     'KRW': '1352.5',
     'KWD': '0.3071',
     'GBP': '0.7893',
     'CLF': '0.02451',
     'CHF': '0.8801'}),
   '30.710'),
  ('control: pound to usd',
   ('5', 'GBP', 'USD',
    {'EUR': '0.92',
     'JPY': '151.37',
     'KRW': '1352.5',
     'KWD': '0.3071',
     'GBP': '0.7893',
     'CLF': '0.02451',
     'CHF': '0.8801'}),
   '6.33'),
  ('control: missing target',
   ('1', 'EUR', 'SEK',
    {'EUR': '0.92',
     'JPY': '151.37',
     'KRW': '1352.5',
     'KWD': '0.3071',
     'GBP': '0.7893',
     'CLF': '0.02451',
     'CHF': '0.8801'}),
   'ERR:no-rate:SEK')],
 [('regression target-exponent 1',
   ('31699.892', 'KWD', 'USD',
    {'EUR': '0.92', 'KRW': '1352.5', 'KWD': '0.3071', 'GBP': '0.7893', 'CLF': '0.02451', 'CHF': '0.8801'}),
   '103223.35'),
  ('regression target-exponent 2',
   ('48429.445', 'EUR', 'KWD',
    {'EUR': '0.92',
     'JPY': '151.37',
     'KRW': '1352.5',
     'KWD': '0.3071',
     'GBP': '0.7893',
     'CLF': '0.02451',
     'CHF': '0.8801'}),
   '16165.959'),
  ('partial repair guard 1',
   ('31654.45', 'KWD', 'CHF',
    {'EUR': '0.92',
     'JPY': '151.37',
     'KRW': '1352.5',
     'KWD': '0.3071',
     'GBP': '-1.2',
     'CLF': '0.02451',
     'CHF': '0.8801',
     'USD': '1'}),
   '90716.64'),
  ('partial repair guard 2',
   ('45677.89', 'GBP', 'KRW',
    {'EUR': '0.92',
     'JPY': '151.37',
     'KRW': '1352.5',
     'KWD': '0.3071',
     'GBP': '0.7893',
     'CLF': '0.02451',
     'CHF': '0.8801',
     'USD': '1'}),
   '78271058'),
  ('control: missing target',
   ('1', 'EUR', 'SEK',
    {'EUR': '0.92',
     'JPY': '151.37',
     'KRW': '1352.5',
     'KWD': '0.3071',
     'GBP': '0.7893',
     'CLF': '0.02451',
     'CHF': '0.8801'}),
   'ERR:no-rate:SEK'),
  ('control: won to franc',
   ('250000', 'KRW', 'CHF',
    {'EUR': '0.92',
     'JPY': '151.37',
     'KRW': '1352.5',
     'KWD': '0.3071',
     'GBP': '0.7893',
     'CLF': '0.02451',
     'CHF': '0.8801'}),
   '162.68'),
  ('control: yen to unit of account',
   ('99999', 'JPY', 'CLF',
    {'EUR': '0.92',
     'JPY': '151.37',
     'KRW': '1352.5',
     'KWD': '0.3071',
     'GBP': '0.7893',
     'CLF': '0.02451',
     'CHF': '0.8801'}),
   '16.1920'),
  ('control: zero rate target', ('10', 'EUR', 'CHF', {'EUR': '0.92', 'CHF': '0'}), 'ERR:bad-rate:CHF')]]
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 target-exponent 1	`16453.26`	`16453`	Failed
regression target-exponent 2	`30.710`	`30.710`	Passed
partial repair guard 2	`63436.470`	`63436.47`	Failed
control: pound to usd	`6.33`	`6.33`	Passed
control: missing target	`ERR:no-rate:SEK`	`ERR:no-rate:SEK`	Passed
control: won to franc	`162.68`	`162.68`	Passed
control: yen to unit of account	`16.1920`	`16.1920`	Passed

SHA-256 / 4e81d2cc407c5e2d3bbf6bd69e0853675baf3dc563e1b9d473af2603efecb68c

3 / The verified repair

Exit 0

"""Failure Map reference implementation. Python standard library only."""
import json
from decimal import Decimal, ROUND_HALF_EVEN, ROUND_HALF_UP, ROUND_FLOOR, ROUND_CEILING, ROUND_DOWN, ROUND_UP, ROUND_HALF_DOWN
N = 1
observations = []
def solve(amount, frm, to, rates):
    exps = {'USD': 2, 'EUR': 2, 'GBP': 2, 'CHF': 2, 'SEK': 2, 'NOK': 2, 'JPY': 0, 'KRW': 0, 'KWD': 3, 'CLF': 4}
    def rate(c):
        if c == 'USD' and c not in rates: return Decimal(1)
        if c not in rates: return None
        return Decimal(rates[c])
    rf, rt = rate(frm), rate(to)
    for c, r in ((frm, rf), (to, rt)):
        if r is None: return 'ERR:no-rate:' + c
        if r <= 0: return 'ERR:bad-rate:' + c
    usd = Decimal(amount) / rf
    out = usd * rt
    return format(out.quantize(Decimal(1).scaleb(-exps[to]), rounding=ROUND_HALF_EVEN), 'f')
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
cases = [[('regression target-exponent 1',
   ('100', 'EUR', 'JPY',
    {'EUR': '0.92',
     'JPY': '151.37',
     'KRW': '1352.5',
     'KWD': '0.3071',
     'GBP': '0.7893',
     'CLF': '0.02451',
     'CHF': '0.8801'}),
   '16453'),
  ('regression target-exponent 2',
   ('100.00', 'USD', 'KWD',
    {'EUR': '0.92',
     'JPY': '151.37',
     'KRW': '1352.5',
     'KWD': '0.3071',
     'GBP': '0.7893',
     'CLF': '0.02451',
     'CHF': '0.8801'}),
   '30.710'),
  ('partial repair guard 2',
   ('19481.34', 'KWD', 'USD',
    {'EUR': '0.92',
     'JPY': '151.37',
     'KRW': '1352.5',
     'KWD': '0.3071',
     'GBP': '0.7893',
     'CLF': '0.02451',
     'CHF': '0.8801'}),
   '63436.47'),
  ('control: pound to usd',
   ('5', 'GBP', 'USD',
    {'EUR': '0.92',
     'JPY': '151.37',
     'KRW': '1352.5',
     'KWD': '0.3071',
     'GBP': '0.7893',
     'CLF': '0.02451',
     'CHF': '0.8801'}),
   '6.33'),
  ('control: missing target',
   ('1', 'EUR', 'SEK',
    {'EUR': '0.92',
     'JPY': '151.37',
     'KRW': '1352.5',
     'KWD': '0.3071',
     'GBP': '0.7893',
     'CLF': '0.02451',
     'CHF': '0.8801'}),
   'ERR:no-rate:SEK'),
  ('control: won to franc',
   ('250000', 'KRW', 'CHF',
    {'EUR': '0.92',
     'JPY': '151.37',
     'KRW': '1352.5',
     'KWD': '0.3071',
     'GBP': '0.7893',
     'CLF': '0.02451',
     'CHF': '0.8801'}),
   '162.68'),
  ('control: yen to unit of account',
   ('99999', 'JPY', 'CLF',
    {'EUR': '0.92',
     'JPY': '151.37',
     'KRW': '1352.5',
     'KWD': '0.3071',
     'GBP': '0.7893',
     'CLF': '0.02451',
     'CHF': '0.8801'}),
   '16.1920')],
 [('regression target-exponent 1',
   ('250000', 'KRW', 'CHF',
    {'EUR': '0.92',
     'JPY': '151.37',
     'KRW': '1352.5',
     'KWD': '0.3071',
     'GBP': '0.7893',
     'CLF': '0.02451',
     'CHF': '0.8801'}),
   '162.68'),
  ('regression target-exponent 2',
   ('99999', 'JPY', 'CLF',
    {'EUR': '0.92',
     'JPY': '151.37',
     'KRW': '1352.5',
     'KWD': '0.3071',
     'GBP': '0.7893',
     'CLF': '0.02451',
     'CHF': '0.8801'}),
   '16.1920'),
  ('partial repair guard 1',
   ('31699.892', 'KWD', 'USD',
    {'EUR': '0.92', 'KRW': '1352.5', 'KWD': '0.3071', 'GBP': '0.7893', 'CLF': '0.02451', 'CHF': '0.8801'}),
   '103223.35'),
  ('partial repair guard 2',
   ('2442.484', 'CHF', 'JPY',
    {'EUR': '0.92', 'JPY': '151.37', 'KWD': '0.3071', 'GBP': '0.7893', 'CLF': '0.02451', 'CHF': '0.8801', 'USD': '1'}),
   '420087'),
  ('control: missing target',
   ('1', 'EUR', 'SEK',
    {'EUR': '0.92',
     'JPY': '151.37',
     'KRW': '1352.5',
     'KWD': '0.3071',
     'GBP': '0.7893',
     'CLF': '0.02451',
     'CHF': '0.8801'}),
   'ERR:no-rate:SEK'),
  ('control: zero rate target', ('10', 'EUR', 'CHF', {'EUR': '0.92', 'CHF': '0'}), 'ERR:bad-rate:CHF'),
  ('control: explicit usd rate', ('10', 'USD', 'EUR', {'USD': '1', 'EUR': '0.92'}), '9.20'),
  ('control: usd absent', ('42.42', 'EUR', 'USD', {'EUR': '0.92'}), '46.11')],
 [('regression target-exponent 1',
   ('113222', 'EUR', 'CLF',
    {'EUR': '0.92', 'JPY': '151.37', 'KWD': '0.3071', 'GBP': '0.7893', 'CLF': '0.02451', 'CHF': '0.8801'}),
   '3016.3818'),
  ('regression target-exponent 2',
   ('19481.34', 'KWD', 'USD',
    {'EUR': '0.92',
     'JPY': '151.37',
     'KRW': '1352.5',
     'KWD': '0.3071',
     'GBP': '0.7893',
     'CLF': '0.02451',
     'CHF': '0.8801'}),
   '63436.47'),
  ('partial repair guard 1',
   ('132236.08', 'CLF', 'KRW', {'EUR': '0.92', 'JPY': '151.37', 'KRW': '1352.5', 'CLF': '0.02451', 'CHF': '0.8801'}),
   '7296992991'),
  ('partial repair guard 2',
   ('23223.04', 'CLF', 'KWD',
    {'EUR': '0.92', 'KRW': '1352.5', 'KWD': '0.3071', 'GBP': '0.7893', 'CLF': '0.02451', 'CHF': '0.8801'}),
   '290974.932'),
  ('control: zero rate target', ('10', 'EUR', 'CHF', {'EUR': '0.92', 'CHF': '0'}), 'ERR:bad-rate:CHF'),
  ('control: explicit usd rate', ('10', 'USD', 'EUR', {'USD': '1', 'EUR': '0.92'}), '9.20'),
  ('control: usd absent', ('42.42', 'EUR', 'USD', {'EUR': '0.92'}), '46.11'),
  ('control: euro to yen',
   ('100', 'EUR', 'JPY',
    {'EUR': '0.92',
     'JPY': '151.37',
     'KRW': '1352.5',
     'KWD': '0.3071',
     'GBP': '0.7893',
     'CLF': '0.02451',
     'CHF': '0.8801'}),
   '16453')],
 [('regression target-exponent 1',
   ('12406.83', 'JPY', 'USD',
    {'EUR': '0.92',
     'JPY': '151.37',
     'KRW': '1352.5',
     'KWD': '0.3071',
     'GBP': '0.7893',
     'CLF': '0.02451',
     'CHF': '0.8801',
     'USD': '1'}),
   '81.96'),
  ('regression target-exponent 2',
   ('69492.535', 'JPY', 'EUR',
    {'EUR': '0.92',
     'JPY': '151.37',
     'KRW': '0',
     'KWD': '0.3071',
     'GBP': '0.7893',
     'CLF': '0.02451',
     'CHF': '0.8801',
     'USD': '1'}),
   '422.36'),
  ('partial repair guard 1',
   ('62580.312', 'CHF', 'KRW',
    {'EUR': '0.92', 'JPY': '151.37', 'KRW': '1352.5', 'KWD': '0.3071', 'GBP': '0.7893', 'CHF': '0.8801'}),
   '96170744'),
  ('partial repair guard 2',
   ('86444.328', 'KWD', 'KRW',
    {'EUR': '0.92', 'JPY': '151.37', 'KRW': '1352.5', 'KWD': '0.3071', 'GBP': '0.7893', 'CLF': '0.02451'}),
   '380709715'),
  ('control: euro to yen',
   ('100', 'EUR', 'JPY',
    {'EUR': '0.92',
     'JPY': '151.37',
     'KRW': '1352.5',
     'KWD': '0.3071',
     'GBP': '0.7893',
     'CLF': '0.02451',
     'CHF': '0.8801'}),
   '16453'),
  ('control: usd to dinar',
   ('100.00', 'USD', 'KWD',
    {'EUR': '0.92',
     'JPY': '151.37',
     'KRW': '1352.5',
     'KWD': '0.3071',
     'GBP': '0.7893',
     'CLF': '0.02451',
     'CHF': '0.8801'}),
   '30.710'),
  ('control: pound to usd',
   ('5', 'GBP', 'USD',
    {'EUR': '0.92',
     'JPY': '151.37',
     'KRW': '1352.5',
     'KWD': '0.3071',
     'GBP': '0.7893',
     'CLF': '0.02451',
     'CHF': '0.8801'}),
   '6.33'),
  ('control: missing target',
   ('1', 'EUR', 'SEK',
    {'EUR': '0.92',
     'JPY': '151.37',
     'KRW': '1352.5',
     'KWD': '0.3071',
     'GBP': '0.7893',
     'CLF': '0.02451',
     'CHF': '0.8801'}),
   'ERR:no-rate:SEK')],
 [('regression target-exponent 1',
   ('31699.892', 'KWD', 'USD',
    {'EUR': '0.92', 'KRW': '1352.5', 'KWD': '0.3071', 'GBP': '0.7893', 'CLF': '0.02451', 'CHF': '0.8801'}),
   '103223.35'),
  ('regression target-exponent 2',
   ('48429.445', 'EUR', 'KWD',
    {'EUR': '0.92',
     'JPY': '151.37',
     'KRW': '1352.5',
     'KWD': '0.3071',
     'GBP': '0.7893',
     'CLF': '0.02451',
     'CHF': '0.8801'}),
   '16165.959'),
  ('partial repair guard 1',
   ('31654.45', 'KWD', 'CHF',
    {'EUR': '0.92',
     'JPY': '151.37',
     'KRW': '1352.5',
     'KWD': '0.3071',
     'GBP': '-1.2',
     'CLF': '0.02451',
     'CHF': '0.8801',
     'USD': '1'}),
   '90716.64'),
  ('partial repair guard 2',
   ('45677.89', 'GBP', 'KRW',
    {'EUR': '0.92',
     'JPY': '151.37',
     'KRW': '1352.5',
     'KWD': '0.3071',
     'GBP': '0.7893',
     'CLF': '0.02451',
     'CHF': '0.8801',
     'USD': '1'}),
   '78271058'),
  ('control: missing target',
   ('1', 'EUR', 'SEK',
    {'EUR': '0.92',
     'JPY': '151.37',
     'KRW': '1352.5',
     'KWD': '0.3071',
     'GBP': '0.7893',
     'CLF': '0.02451',
     'CHF': '0.8801'}),
   'ERR:no-rate:SEK'),
  ('control: won to franc',
   ('250000', 'KRW', 'CHF',
    {'EUR': '0.92',
     'JPY': '151.37',
     'KRW': '1352.5',
     'KWD': '0.3071',
     'GBP': '0.7893',
     'CLF': '0.02451',
     'CHF': '0.8801'}),
   '162.68'),
  ('control: yen to unit of account',
   ('99999', 'JPY', 'CLF',
    {'EUR': '0.92',
     'JPY': '151.37',
     'KRW': '1352.5',
     'KWD': '0.3071',
     'GBP': '0.7893',
     'CLF': '0.02451',
     'CHF': '0.8801'}),
   '16.1920'),
  ('control: zero rate target', ('10', 'EUR', 'CHF', {'EUR': '0.92', 'CHF': '0'}), 'ERR:bad-rate:CHF')]]
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 target-exponent 1	`16453`	`16453`	Passed
regression target-exponent 2	`30.710`	`30.710`	Passed
partial repair guard 2	`63436.47`	`63436.47`	Passed
control: pound to usd	`6.33`	`6.33`	Passed
control: missing target	`ERR:no-rate:SEK`	`ERR:no-rate:SEK`	Passed
control: won to franc	`162.68`	`162.68`	Passed
control: yen to unit of account	`16.1920`	`16.1920`	Passed

SHA-256 / d21be57b2aaa75cdc2c20410878fc459ef7cf8e3f01b340cdf3da5f96e95fd92

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 2026-09-29T14:46:59.351272+00:00.

Case digest / 7ec356ccb1d462428657017997fd328855908f3ffc3ffcb668c1c1b7bbaf080e