package calculator.model;

import java.util.*;

/**
 * A wrapper around java.util.Stack use to provide stack of Operation objects.
 */
public class OperandStack
{
    /**
     * Add operand to the top of stack.
     */
    public void push(double operand)
    {
        // throw an exception if the value is not valid or +/- infinite
        if (Double.isNaN(operand))
            throw new OperationParameterException("Result of function is undefined.");

        if (operand == Double.POSITIVE_INFINITY)
            throw new OperationParameterException("Infinity");

        if (operand == Double.NEGATIVE_INFINITY)
            throw new OperationParameterException("-Infinity");

        operandStack.push(new Double(operand));
    }

    /**
     * Remove operand from the top of stack.
     */
    public double pop()
    {
        return ((Double)operandStack.pop()).doubleValue();
    }

    /**
     * Peek the value at the top without removing it.
     */
    public double peek()
    {
        return ((Double)operandStack.peek()).doubleValue();
    }

    /**
     * Clear the stack
     */
    public void clear()
    {
        operandStack.clear();
    }

    // The inner stack object
    private Stack operandStack = new Stack();
}