Data.Scientific provides a space efficient and arbitrary precision
scientific number type.

Scientific numbers are represented using
scientific notation. It
uses a coefficient c :: Integer and a base-10 exponent e :: Int (do
note that since we're using an Int to represent the exponent these numbers
aren't truly arbitrary precision). A scientific number corresponds to the
Fractional number: fromInteger c * 10 ^^ e.

The main application of Scientific is to be used as the target of parsing
arbitrary precision numbers coming from an untrusted source. The advantages
over using Rational for this are that:

A Scientific is more efficient to construct. Rational numbers need to be
constructed using % which has to compute the gcd of the numerator and
denominator.

Scientific is safe against numbers with huge exponents. For example:
1e1000000000 :: Rational will fill up all space and crash your
program. Scientific works as expected:

Also, the space usage of converting scientific numbers with huge exponents to
Integrals (like: Int) or RealFloats (like: Double or Float)
will always be bounded by the target type.