Java Math Expressions Parser supports BigInteger, BigDecimal, rational, complex, vector/matrix/tensor expressions. Just added JSR-223 script engine for that. As usual, the sources are available at http://scripting.dev.java.net.
I'd like to add a script engine (or extend one of the existing engines like JEP engine) to support interval arithmetic. I came across Frink - but it is not open source (nor the interfaces seem available). Other library that I came across is this: http://interval.sourceforge.net.