BigDecimal provides arbitrary-precision floating point decimal arithmetic
Description
Ruby provides built-in support for arbitrary precision integer arithmetic.
42**13 -> 1265437718438866624512
BigDecimal provides similar support for very large or very accurate floating
point numbers. Decimal arithmetic is also useful for general calculation,
because it provides the correct answers people expect–whereas normal binary
floating point arithmetic often introduces subtle errors because of the
conversion between base 10 and base 2.
