FA-61889 / Currency rounding and FX conversion / Member archive

Conversions involving USD require an explicit USD table entry · case 04

USD to EUR fails with ERR:no-rate:USD even though USD is the pivot currency.

Member previewVariant 4 · 3 implementations · 8 checks per implementation

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.

One recorded failure

Sample boundary fixture

This sample comes from the broken implementation of a controlled reproducer.

Boundary fixture	Actual	Expected	Outcome
regression implicit-usd 1	`"ERR:no-rate:USD"`	`"31474.00"`	Failed

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