package calculator.operations;
   
   import java.util.List;
   
   import calculator.Expression;
   import calculator.IllegalConstruction;
   import calculator.atoms.Complex;
   import calculator.atoms.IntegerAtom;
   import calculator.atoms.Rationnal;
  import calculator.atoms.Real;
  
  /**
   * This class represents the arithmetic operation "-".
   * The class extends an abstract superclass Operation.
   * Other subclasses of Operation represent other arithmetic operations.
   * 
   * @see Operation
   * @see Plus
   * @see Times
   * @see Divides
   */
  public final class Minus extends Operation {
  
  	/**
  	 * Class constructor specifying a number of Expressions to subtract.
  	 *
  	 * @param elist The list of Expressions to subtract
  	 * @throws IllegalConstruction If an empty list of expressions if passed as
  	 *                             parameter
  	 * @see #Minus(List<Expression>)
  	 */
  	public Minus(List<Expression> elist) throws IllegalConstruction {
  		super(elist);
  		symbol = "-";
  		neutral = 0;
  	}
  
  	/**
  	 * The actual computation of the (binary) arithmetic subtraction of two integers
  	 * 
  	 * @param l The first integer
  	 * @param r The second integer that should be subtracted from the first
  	 * @return The integer that is the result of the subtraction
  	 */
  	public int op(int l, int r) {
  		return (l - r);
  	}
  
  	/**
  	 * The actual computation of the (binary) arithmetic subtraction of two Reals
  	 * 
  	 * @param r1 The first Real
  	 * @param r2 The second Real
  	 * @return The (new) Real that is the result of the subtraction
  	 */
  	public Real op(Real r1, Real r2) {
  
  		if ((r1.isPlusInf() && r2.isPlusInf())
  				|| (r1.isMinusInf() && r2.isMinusInf())
  				|| r1.isNan() || r2.isNan()) { // inf-inf = NaN or NaN + x = NaN
  			return Real.nan();
  		}
  		if (r1.isMinusInf() || r2.isPlusInf()) { // x - inf = -inf
  			return Real.minusInf();
  		}
  		if (r1.isPlusInf() || r2.isMinusInf()) { // x + inf = +inf
  			return Real.plusInf();
  		}
  
  		return new Real(r1.getValue().add(r2.getValue().negate()));
  	}
  
  	/**
  	 * The actual computation of the (binary) arithmetic subtraction of two
  	 * Integers
  	 * 
  	 * @param i1 The first IntegerAtom
  	 * @param i2 The second IntegerAtom
  	 * @return The (new) IntegerAtom that is the result of the subtraction
  	 */
  	public IntegerAtom op(IntegerAtom i1, IntegerAtom i2) {
  		return new IntegerAtom(i1.getValue() - i2.getValue());
  	}
  
  	@Override
  	public Complex op(Complex c1, Complex c2) {
  		if (c1.isNaN() || c2.isNaN()) {
  			return Complex.nan();
  		}
  		org.apache.commons.numbers.complex.Complex result = c1.getValue().subtract(c2.getValue());
  		return new Complex(result);
  	}
  
  	@Override
  	public Rationnal op(Rationnal q1, Rationnal q2) {
  		org.apache.commons.numbers.fraction.Fraction result = q1.getValue().subtract(q2.getValue());
  		return new Rationnal(result);
  	}
  }