Como Usar Funções Customizadas com a exp4j

Com withCustomFunction

import static java.lang.System.out;

import de.congrace.exp4j.Calculable;
import de.congrace.exp4j.CustomFunction;
import de.congrace.exp4j.ExpressionBuilder;

public final class Exp4jSample {

  public static void main(final String[] args) throws Exception {
    final Calculable calc = new ExpressionBuilder("sample(1, 1)").withCustomFunction(new CustomFunction("sample", 2) {

      @Override
      public double applyFunction(final double... args) {
        return args[0] + args[1];
      }

    }).build();

    out.println(calc.calculate());
  }

}

Com withCustomFunctions

import static java.lang.System.out;

import java.util.ArrayList;
import java.util.Collection;

import de.congrace.exp4j.Calculable;
import de.congrace.exp4j.CustomFunction;
import de.congrace.exp4j.ExpressionBuilder;

public final class Exp4jSample {

  public static void main(final String[] args) throws Exception {
    final Collection<CustomFunction> funcLst = new ArrayList<CustomFunction>();

    funcLst.add(new CustomFunction("sample", 2) {

      @Override
      public double applyFunction(final double... args) {
        return args[0] + args[1];
      }

    });
    
    final Calculable calc = new ExpressionBuilder("sample(1, 1)").withCustomFunctions(funcLst).build();

    out.println(calc.calculate());
  }

}

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