The annuity function is used to compute the present or future value of an ordinary annuity. Rate is the interest rate per period, and periods is the number of periods over which the value is calculated. The formula for annuity is: annuity (rate, periods) = (1 - (1+rate) periods) / rate The annuity function is more accurate than computing the formula above using basic arithmetic operations and exponentiation, especially when rate is small.

---

Examples:

on mouseUp
    put myPayment*annuity(.015,12) into presentValue
    put myPayment*annuity(.015,12)*compound(.015,12) into futureValue
end mouseUp

Usage:

Rate and periods are expressions that yield numbers.

on mouseUp
    annuity({rate},{periods})
end mouseUp