See: Description
| Package | Description |
|---|---|
| de.congrace.exp4j |
Calculable calc = new ExpressionBuilder("3 * sin(y) - 2 / (x - 2)").withVariable("x", varX).withVariable("y", varY).build()
double result1=calc.calculate();
you can also change variables values after building by invoking Calculable.setVariable(String varName,double value),
but one has to make sure that the variable names are passed into the ExpressionBuilder using at
least ExpressionBuilder.withVariableNames(String...). If variables are used in the expression without setting at least their names,
an UnparseableExpressionException will be thrown.
Calculable calc = new ExpressionBuilder("x * y - 2").withVariableNames("x","y").build();
calc.setVariable("x",1);
calc.setVariable("x",2);
assertTrue(calc.calculate()==0);
Using custom functions
CustomFunction fooFunc = new CustomFunction("foo") {
public double applyFunction(double value) {
return value*Math.E;
}
};
double varX=12d;
Calculable calc = new ExpressionBuilder("foo(x)").withCustomFunction(fooFunc).withVariable("x",varX).build();
assertTrue(calc.calculate() == Math.E * varX);
Using custom operators
CustomOperator greaterEq = new CustomOperator(">=", true, 4, 2) {
double applyOperation(double[] values) {
if (values[0] >= values[1]){
return 1d;
}else{
return 0d;
}
}
};
Calculable calc = new ExpressionBuilder("1>=2").withOperation(greaterEq).build();
assertTrue(0d == calc.calculate());
Operators and functionsCopyright © 2013. All Rights Reserved.