Is 128-bit "long-float" useful? [closed]

Question

I realized the other day that most common lisp had 128-bit "long-floats". As a result, the most positive long float is:

8.8080652584198167656 * 10^646456992

while the most positive double float is 1.7976931348623157 * 10^308, which is pretty big already.

I wanted to know whether anyone had ever needed a number bigger than 1.7976931348623157 * 10^308, and if so, in which condition?

Do you feel it is useful to have by default in a programming language?

Is the precision of a 64-bit double float not enough in some circumstances? I would love to hear use-cases.

Answer 1

I guess the advantage of long floats is not only that they can span huge ranges, which may or may not be useful, they probably also have a much larger mantissa (I refuse to use the word "significand" for this) than a double, which gives your numbers a higher precision.

But as someone said, scientists love those types. Probably for the above reason. Note that the libraries are often called arbitrary precision libraries.

Answer 2

Scientists use this kind of stuff - and occasionally arbitrarily sized integers/floats/decimals.

For you, 32-bit or 64-bit is usually enough.

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See also:

http://en.wikipedia.org/wiki/Arbitrary-precision_arithmetic