Add specific return type

[n-arms]

Description

Instead of having a hard evaluation (<ExpressionSyntax.approximate()>) return an instance of Java.lang.Object, it would make sense to return a custom return type, especially to help with complex numbers (#4 ).

Implementation

The return type would need to support:

• [x] Casting to raw java primitives (bool, double, float, int, long, etc)
• [ ] Dynamic precision numbers
• [x] NaN
• [x] +/- Infinity
• [x] operations like *, ^, +, <, etc
• [x] Complex numbers