FA-63448 / Actuarial life tables / Member archive

Commutation-function life annuities: Temporary annuities stop one payment early · case 03

An n-year annuity-due makes n-1 payments.

Member previewVariant 3 · 3 implementations · 8 checks per implementation

Case contract

Input l by age from 0, i (per mille), age, n (None = whole life). v=1/(1+i); D_k = v^k l_k (zero beyond the table); N_k = sum of D from k. end = table length for whole life else min(length, age+n). Annuity-due = (N_age - N_end)/D_age; immediate = (N_{age+1} - N_{end+1})/D_age. Missing or extinct age -> 'invalid age'. Return both rounded to 6.

Why this case matters

Life-table arithmetic compounds across ages, so one misplaced index or assumption shifts every downstream value.

One recorded failure

Sample boundary fixture

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

Boundary fixture	Actual	Expected	Outcome
temporary annuity 0	`[1.0, 0.962112]`	`[1.962112, 1.886656]`	Failed

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