Module rule_of_72 

Approximate years to double (Rule of 72 / 69 / 70) and exact doubling time.

Prefer doubling_solution for formulas, comparison tables, and multi-rate scenarios. Prefer doubling_time when you only need the exact discrete result.

Error handling (v0.1+)

All public entry points return FinanceResult. Zero or negative rates and non-finite inputs yield FinanceError — they do not panic.

Structs

DoublingRateRow

One row of a multi-rate doubling comparison.

DoublingRateSeries

Table of doubling estimates across many rates (teaching: when is Rule of 72 “good enough?”).

DoublingSolution

Comparison of doubling-time methods at a single rate.

Functions

doubling_compare_rates

Compare doubling rules across a list of rates (teaching: when is Rule of 72 “good enough?”).

doubling_solution

Build a DoublingSolution comparing Rule of 72/70/69 with exact discrete and continuous times.

doubling_time

Exact periods to double under discrete compounding: ln(2) / ln(1 + rate).

doubling_time_continuous

Exact time to double under continuous compounding: ln(2) / rate.

rule_of_69

Approximate years to double using the Rule of 69: 69 / (100 * rate).

rule_of_70

Approximate years to double using the Rule of 70: 70 / (100 * rate).

rule_of_72

Approximate years to double using the Rule of 72: 72 / (100 * rate).