Calculator: A Java repository from ylfzq

How to compile using gradle

Step 1. Add the JitPack repository to your build file

Add it in your root build.gradle at the end of repositories:

allprojects {
    repositories {
        ...
	maven { url 'https://jitpack.io' }
    }
}

Step 2. Add the dependency

dependencies {
    compile 'com.github.ylfzq:Calculator:*'
}

The latest release is:

How to use

Simple usage is:

System.out.println(
    Calculator.getDefault().calcExpression("1+2*(3+4*6)/min(5, 2, PI)")
);

which outputs 28.0 as result.

You can print calculate steps to PrintStream by

System.out.println(
	Calculator.getDefault()
    .setCalcStepPrintStream(System.err)		// print calculate steps to System.err
    .calcExpression("1+2*(3+4*6)/min(5, 2, PI)")
);

the output is:

4.0*6.0=24.0
3.0+24.0=27.0
2.0*27.0=54.0
PI=3.141592653589793
min(5.0,2.0,3.141592653589793)=2.0
54.0/2.0=27.0
1.0+27.0=28.0
28.0

How to extend

We call all operands, functions and constants as "CalcUnit". CalcUnit's hierarchy:

CalcUnit
|-- ConstantCalcUnit
|-- FunctionCalcUnit
|-- OperatorCalcUnit
    |-- SingleOperandOperatorCalcUnit
    |-- TwoOperandsOperatorCalcUnit

You can call Calculator.addCalcUnit(CalcUnit[]) to add custom implemented CalcUnit. For example:

Calculator.getDefault().addCalcUnit(new CalcUnit[] {
	new ConstantCalcUnit("e", 2.718281828),
	new ConstantCalcUnit("g", 9.8),
	new FunctionCalcUnit("sqrt") {	// define function named sqrt
      @Override public Number doCalc(Number... vals) {
        if (vals.length > 1) {
          throw new IllegalArgumentException("sqrt() can only receive 1 param");
        }

        return Math.sqrt(vals[0].doubleValue());
      }
    },
    new TwoOperandsOperatorCalcUnit("**", CalcUnitsImpl.CALC_LEVEL_MULTIPLY_DIVID + 1) {
      @Override public Number doCalc(Number val1, Number val2) {
        return Math.pow(val1.doubleValue(), val2.doubleValue());
      }
    }
});

extend Constant

// The first param is the constant name, the second param is the constant value
new ConstantCalcUnit("e", 2.718281828);

extend Function

new FunctionCalcUnit("sqrt") {	// define function named sqrt
  @Override public Number doCalc(Number[] vals) {	// the function params, you can throw if the param count is not correct
    if (vals.length > 1) {
      throw new IllegalArgumentException("sqrt() can only receive 1 param");
    }

    return Math.sqrt(vals[0].doubleValue());
  }
}

extend Operator

There are 3 types of Operators: left-single-operand operator, right-single-operand operator, two operands operator.

// define a factorial operator "!", the second param true stands the operand is left to operator, otherwise is stands right operand.
public static final CalcUnit OPERATOR_FACTORIAL = new SingleOperandOperatorCalcUnit("!", true) {
    @Override public Number doCalc(Number val) {
      double mul = 1;
      int a = val.intValue();
      for (int i = 2; i <= a; ++i) {
        mul *= i;
      }
      return mul;
    }
  };

How to debug

Call setStackPrintStream(PrintStream) or setCalcStepPrintStream(PrintStream) on Calculator to print steps.

System.out.println(
    Calculator.getDefault()
    .setStackPrintStream(System.err)
    .calcExpression("1+2*(3+4*6)/min(5, 2, PI)")
);

[]
[1.0]

[+]
[1.0]

[+]
[2.0, 1.0]

[*, +]
[2.0, 1.0]

[(, *, +]
[2.0, 1.0]

[(, *, +]
[3.0, 2.0, 1.0]

[+, (, *, +]
[3.0, 2.0, 1.0]

[+, (, *, +]
[4.0, 3.0, 2.0, 1.0]

[*, +, (, *, +]
[4.0, 3.0, 2.0, 1.0]

[*, +, (, *, +]
[6.0, 4.0, 3.0, 2.0, 1.0]

[*, +]
[27.0, 2.0, 1.0]

[/, +]
[54.0, 1.0]

[min, /, +]
[(, 54.0, 1.0]

[(, min, /, +]
[(, 54.0, 1.0]

[(, min, /, +]
[5.0, (, 54.0, 1.0]

[(, min, /, +]
[5.0, (, 54.0, 1.0]

[(, min, /, +]
[2.0, 5.0, (, 54.0, 1.0]

[(, min, /, +]
[2.0, 5.0, (, 54.0, 1.0]

[(, min, /, +]
[3.141592653589793, 2.0, 5.0, (, 54.0, 1.0]

[/, +]
[2.0, 54.0, 1.0]