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📁 C ++ in action
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<h3>Exercise Solutions</h3>
<ol>

<li> The first solution is to create the two worlds in a loop:
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<pre>for (int i = 1; i &lt; 3; ++i)
    World world (i);
</pre>
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The second possibility is to open a separate local scope for each world:
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<pre>int main ()
{
    {
        World world (1);
    }
    {
        World world (2);
    }
}</pre>
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<li> The problem is in the order of initialization of data members. Despite the ordering of initializers in the preamble to the constructor, _hand will be initialized before _n because that抯 the order in which they are embedded in Glove. Therefore _n shouldn抰 be passed as an argument to the Hand抯 constructor because its value hasn抰 been set at that point. One way of fixing this bug is to change the order of embeddings. The other is to use numFingers instead of _n to initialize the _hand.
<li> Bars.
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<pre>class HorBar
{
public:
    HorBar (int n)
    {
        std::cout &lt;&lt; "+";
        for (int i = 0; i &lt; n; ++i)
            std::cout &lt;&lt; "-";
        std::cout &lt;&lt; "+\n";
    }
};

class VerBar
{
public:
    VerBar (int n)
    {
        for (int i = 0; i &lt; n; ++i)
            std::cout &lt;&lt; "|\n";
    }
};

class Frame
{
public:
    Frame (int hor, int ver)
    : _upper (hor),
      _ver (ver),
      _lower (hor)
    {}
private:
    HorBar _upper;
    VerBar _ver;
    HorBar _lower;
};</pre>
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<li> Ladder
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<pre>class Ladder
{
public:
    Ladder (int hor, int ver)
    : _upper (hor, ver),
      _middle (ver),
      _lower (hor, ver)
    {}
private:
    Frame                _upper;
    VerBar                _middle;
    Frame                _lower;
};
</pre>
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<li> This particular solution that uses only the constructs introduced in chapter 1. 
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<pre>int main ()
{
    InputNum num;
    int factorial = 1;
    for (int i = 2; i &lt; num.GetValue (); ++i)
        factorial = factorial * i;
    factorial = factorial * num.GetValue ();
    std::cout &lt;&lt; num.GetValue () &lt;&lt; "! = " 
                        &lt;&lt; factorial &lt;&lt; std::endl;
}</pre>
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<li>Planet
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<pre>class Planet: public CelestialBody
{
public:
    Planet (double mass, double albedo)
        : CelestialBody (mass),
          _albedo (albedo)
    {
        std::cout &lt;&lt; "Creating a planet with albedo "
                &lt;&lt; _albedo &lt;&lt; std::endl;
    }
    ~Planet ()
    {
        std::cout &lt;&lt; "Destroying a planet with albedo "
                &lt;&lt; _albedo &lt;&lt; std::endl;
    }
private:
    double _albedo;
};
</pre>
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<li> The first part:
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<pre>class Two
{
public:
    Two ()
    {
        std::cout &lt;&lt; "Program ";
    }
};

class Three
{
public:
    Three ()
    {
        std::cout &lt;&lt; "objects ";
    }
};

class Four
{
public:
    Four ()
    {
        std::cout &lt;&lt; "makes ";
    }
};

class One: public Two
{
public:
    One ()
    {
        Three three;
        std::cout &lt;&lt; "with class. ";
    }
private:
    Four    _four;
};
</pre>
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The second part can be implemented like this:
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<pre>class One: public Two
{
public:
    One ()
    {
        std::cout &lt;&lt; "class ";
    }
    ~One ()
    {
        std::cout &lt;&lt; "class ";
    }
private:
    Three            _three;
    Four            _four;
    Five            _five;
};

int main ()
{
    One one;
    std::cout &lt;&lt; std::endl;
}
</pre>
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where the classes Two, Three, Four and Five print 揚rogram
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