FA-58793 / Loan amortization schedules / Member archive

Credit line average daily balance: event effective day · case 03

Draws accrue no interest on the day they are taken.

Member previewVariant 3 · 3 implementations · 7 checks per implementation

Case contract

x = {'rate_bp', 'basis', 'start_balance', 'cycle_days', 'events': [[day 1..cycle_days, signed amount]], 'min_bp', 'min_floor'}. Events take effect at the start of their day. Each day adds max(balance, 0) to the accumulator; interest = round_half_up(acc*bp/(10000*basis)) once per cycle. owed = end balance + interest. Minimum = 0 if owed <= 0 else min(owed, max(min_floor, interest + round_half_up(max(end balance, 0)*min_bp/10000))). Return {'interest', 'balance': owed, 'minimum', 'adb': acc // cycle_days}.

Why this case matters

Amortization engines drive borrower statements, payoff quotes and investor remittances; a misplaced rounding step, boundary or ordering rule compounds across hundreds of periods.

One recorded failure

Sample boundary fixture

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

Boundary fixture	Actual	Expected	Outcome
regression: event effective day	`{"adb": 1003571, "balance": 1009619, "interest": 4619, "minimum": 14669}`	`{"adb": 1003750, "balance": 1009620, "interest": 4620, "minimum": 14670}`	Failed

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