How to calculate use BigDecimal?

[xjl456852]

calculate the following,the result is wroing
Scope scope = new Scope();
Variable a = scope.create("a");
Expression expr = Parser.parse("a + 2.4", scope);
a.setValue(1.2);
double evaluate = expr.evaluate();
System.out.println(evaluate);

the result is 3.5999999999999996

How to calculate use BigDecimal , then result is 3.6 ?

[elmuerte]

You cannot. I've created a fork which uses BigDecimal instead of double as its basis: bdparsii
Using BigDecimal does have its price, it's about 10 times slower to perform the calculations. That's simply the due to the arbitrary precision of BigDecimals, the rest of parsii's fastness is still there.

Note, the port is not production tested, requires java 8 and brings in a dependency: obermuhlner's big-math.