Brobdingnag (version 1.2-9)

Brobdingnag-package: tools:::Rd_package_title("Brobdingnag")

Description

tools:::Rd_package_description("Brobdingnag")

Author

tools:::Rd_package_author("Brobdingnag")

Maintainer: tools:::Rd_package_maintainer("Brobdingnag")

Details

The DESCRIPTION file: tools:::Rd_package_DESCRIPTION("Brobdingnag") tools:::Rd_package_indices("Brobdingnag") Real numbers are represented by two objects: a real, holding the logarithm of their absolute values; and a logical, indicating the sign. Multiplication and exponentiation are easy: the challenge is addition. This is achieved using the (trivial) identity \(\log(e^x+e^y)=x+\log(1+e^{y-x})\) where, WLOG, \(y<x\).

Complex numbers are stored as a pair of brobs: objects of class glub.

The package is a simple example of S4 methods.

However, it could be viewed as a cautionary tale: the underlying R concepts are easy yet the S4 implementation is long and difficult. I would not recommend using S4 methods for a package as simple as this; S3 methods would have been perfectly adequate. I would suggest that S4 methods should only be used when S3 methods are demonstrably inadequate.

References

R. K. S. Hankin 2007. “Very Large Numbers in R: Introducing Package Brobdingnag”. R News, volume 7, number 3, pages 15-16

Examples

googol <- as.brob(10)^100

googol
googol + googol/2

1/(googol + 1e99)

(1:10)^googol

googolplex <- 10^googol

googolplex

googolplex * googol  # practically the same as googolplex (!)