Java BigDecimal trigonometric methods

Question

I am developing a mathematical parser which is able to evaluate String like \'5+b*sqrt(c^2)\'. I am using ANTLR for the parsing and make good progress. Now I fe

Answer 1

The big-math library provides all the standard advanced mathematical functions (pow, sqrt, log, sin, ...) for BigDecimal.

https://github.com/eobermuhlner/big-math

Answer 2

Using an existing feature of Java BigDecimals, namely to allow limited precision arithmetic as described here, I recently implemented sqrt/1, exp/1, tan/1, etc.. for these number objects.

The numeric algorithms themselve use Maclaurin and Taylor series, plus appropriate range reductions to assure enough speed and breadth of the series.

Here is an example calculation, Ramanujan's Constant:

Jekejeke Prolog 2, Runtime Library 1.1.8
(c) 1985-2017, XLOG Technologies GmbH, Switzerland

?- use_module(library(stream/console)).
% 0 consults and 0 unloads in 0 ms.
Yes

?- X is mp(exp(pi*sqrt(163)), 60).
X = 0d262537412640768743.999999999999250072597198185688879353856320

The thingy was written in mixture of Prolog and Java. The speed and accuracy of it is still work in progress. The code is currently open source on GitHub.

Answer 3

ApFloat is a library which contains arbitrary-precision approximations of trigometric functions and non-integer powers both; however, it uses its own internal representations, rather than BigDecimal and BigInteger. I haven't used it before, so I can't vouch for its correctness or performance characteristics, but the api seems fairly complete.

Answer 4

Pretty much the best book on Numerical Computing would be Numerical Recipes

Answer 5

BigDecimal does not provide these methods because BigDecimal models a rational number. Trigonometric functions, square roots and powers to non-integers (which I guess includes square roots) all generate irrational numbers.

These can be approximated with an arbitrary-precision number but the exact value can't be stored in a BigDecimal. It's not really what they're for. If you're approximating something anyway, you may as well just use a double.