commit the codes of chapter08

source/chapter08/arrtemp.cpp

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+// arrtemp.cpp -- using template functions with array template
+#include <iostream>
+#include <array>
+#include <string>
+template <class T, size_t n>
+void display(const std::array<T, n> & ar);
+int main()
+{
+	std::array<int, 5> ai = {1,2,3,4,5}; //,6,7,8,9,22};
+	std::array<std::string, 5> as =
+	{
+		"string under construction",
+		"stupid string indeed",
+		"there's nothing to see",
+		"nothing to do",
+		"but enjoy all that is"
+	};
+	display(ai);
+	display(as);
+	// std::cin.get();
+	return 0;
+}
+template <class T, size_t n>
+void display(const std::array<T,  n> & ar)
+{
+	for (int i = 0; i < 5; i++)
+		std::cout << ar[i] << std::endl;
+}

source/chapter08/choices.cpp

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+// choices.cpp -- choosing a template
+#include <iostream>
+
+template<class T>
+T lesser(T a, T b)         // #1
+{
+    return a < b ? a : b;
+}
+
+int lesser (int a, int b)  // #2
+{
+    a = a < 0 ? -a : a;
+    b = b < 0 ? -b : b;
+    return a < b ? a : b;
+}
+
+int main()
+{
+    using namespace std;
+    int m = 20;
+    int n = -30;
+    double x = 15.5;
+    double y = 25.9;
+
+    cout << lesser(m, n) << endl;       // use #2
+    cout << lesser(x, y) << endl;       // use #1 with double
+    cout << lesser<>(m, n) << endl;     // use #1 with int
+    cout << lesser<int>(x, y)  << endl; // use #1 with int
+
+    // cin.get();
+    return 0;
+}

source/chapter08/cubes.cpp

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+// cubes.cpp -- regular and reference arguments
+#include <iostream>
+double cube(double a);
+double refcube(double &ra);
+int main ()
+{
+    using namespace std;
+    double x = 3.0;
+
+    cout << cube(x);
+    cout << " = cube of " << x << endl;
+    cout << refcube(x);
+    cout << " = cube of " << x << endl;
+    // cin.get();
+    return 0;
+}
+
+double cube(double a)
+{
+    a *= a * a;
+    return a;
+}
+
+double refcube(double &ra)
+{
+    ra *= ra * ra;
+    return ra; 
+}

source/chapter08/filefunct.cpp

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+//filefunc.cpp -- function with ostream & parameter
+#include <iostream>
+#include <fstream>
+#include <cstdlib>
+using namespace std;
+
+void file_it(ostream & os, double fo, const double fe[],int n);
+const int LIMIT = 5;
+int main()
+{
+    ofstream fout;
+    const char * fn = "ep-data.txt";
+    fout.open(fn);
+    if (!fout.is_open())
+    {
+        cout << "Can't open " << fn << ". Bye.\n";
+        exit(EXIT_FAILURE);
+    }
+    double objective;
+    cout << "Enter the focal length of your "
+            "telescope objective in mm: ";
+    cin >> objective;
+    double eps[LIMIT];
+    cout << "Enter the focal lengths, in mm, of " << LIMIT
+         << " eyepieces:\n";
+    for (int i = 0; i < LIMIT; i++)
+    {
+        cout << "Eyepiece #" << i + 1 << ": ";
+        cin >> eps[i];
+    }
+    file_it(fout, objective, eps, LIMIT);
+    file_it(cout, objective, eps, LIMIT);
+    cout << "Done\n";
+    // cin.get();
+    // cin.get();
+    return 0;
+}
+
+void file_it(ostream & os, double fo, const double fe[],int n)
+{
+    // save initial formatting state
+    ios_base::fmtflags initial;
+    initial = os.setf(ios_base::fixed, ios_base::floatfield);
+    std::streamsize sz = os.precision(0);
+    os << "Focal length of objective: " << fo << " mm\n";
+    os.precision(1);
+    os.width(12);
+    os << "f.l. eyepiece";
+    os.width(15);
+    os << "magnification" << endl;
+    for (int i = 0; i < n; i++)
+    {
+        os.width(12);
+        os << fe[i];
+        os.width(15);
+        os << int (fo/fe[i] + 0.5) << endl;
+    }
+    // restore initial formatting state
+    os.setf(initial, ios_base::floatfield);
+    os.precision(sz);
+}

source/chapter08/firstref.cpp

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+// firstref.cpp -- defining and using a reference
+#include <iostream>
+int main()
+{
+    using namespace std;
+    int rats = 101;
+    int & rodents = rats;   // rodents is a reference
+
+    cout << "rats = " << rats;
+    cout << ", rodents = " << rodents << endl;
+    rodents++;
+    cout << "rats = " << rats;
+    cout << ", rodents = " << rodents << endl;
+
+// some implementations require type casting the following
+// addresses to type unsigned
+    cout << "rats address = " << &rats;
+    cout << ", rodents address = " << &rodents << endl;
+    // cin.get();
+    return 0; 
+}

source/chapter08/funtemp.cpp

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+// funtemp.cpp -- using a function template
+#include <iostream>
+// function template prototype
+template <typename T>  // or class T
+void Swap(T &a, T &b);
+
+int main()
+{
+    using namespace std;
+    int i = 10;
+    int j = 20;
+    cout << "i, j = " << i << ", " << j << ".\n";
+    cout << "Using compiler-generated int swapper:\n";
+    Swap(i,j);  // generates void Swap(int &, int &)
+    cout << "Now i, j = " << i << ", " << j << ".\n";
+
+    double x = 24.5;
+    double y = 81.7;
+    cout << "x, y = " << x << ", " << y << ".\n";
+    cout << "Using compiler-generated double swapper:\n";
+    Swap(x,y);  // generates void Swap(double &, double &)
+    cout << "Now x, y = " << x << ", " << y << ".\n";
+    // cin.get();
+    return 0;
+}
+
+// function template definition
+template <typename T>  // or class T
+void Swap(T &a, T &b)
+{
+    T temp;   // temp a variable of type T
+    temp = a;
+    a = b;
+    b = temp; 
+}

source/chapter08/inline.cpp

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+// inline.cpp -- using an inline function
+#include <iostream>
+
+// an inline function definition
+inline double square(double x) { return x * x; }
+int main()
+{
+    using namespace std;
+    double a, b;
+    double c = 13.0;
+
+    a = square(5.0);
+    b = square(4.5 + 7.5);   // can pass expressions
+    cout << "a = " << a << ", b = " << b << "\n";
+    cout << "c = " << c;
+    cout << ", c squared = " << square(c++) << "\n";
+    cout << "Now c = " << c << "\n";
+    // cin.get();
+    return 0;  
+}

source/chapter08/left.cpp

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+// left.cpp -- string function with a default argument
+#include <iostream>
+const int ArSize = 80;
+char * left(const char * str, int n = 1);
+int main()
+{
+    using namespace std;
+    char sample[ArSize];
+    cout << "Enter a string:\n";
+    cin.get(sample,ArSize);
+    char *ps = left(sample, 4);
+    cout << ps << endl;
+    delete [] ps;       // free old string
+    ps = left(sample);
+    cout << ps << endl;
+    delete [] ps;       // free new string
+    // cin.get();
+    // cin.get();
+    return 0;
+}
+
+// This function returns a pointer to a new string
+// consisting of the first n characters in the str string.
+char * left(const char * str, int n)
+{
+    if(n < 0)
+        n = 0;
+    char * p = new char[n+1];
+    int i;
+    for (i = 0; i < n && str[i]; i++)
+        p[i] = str[i];  // copy characters
+    while (i <= n)
+        p[i++] = '\0';  // set rest of string to '\0'
+    return p; 
+}

source/chapter08/leftover.cpp

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+// leftover.cpp -- overloading the left() function
+#include <iostream>
+unsigned long left(unsigned long num, unsigned ct);
+char * left(const char * str, int n = 1);
+
+int main()
+{
+     using namespace std;
+    char * trip = "Hawaii!!";   // test value
+    unsigned long n = 12345678; // test value
+    int i;
+    char * temp;
+
+    for (i = 1; i < 10; i++)
+    {
+        cout << left(n, i) << endl;
+        temp = left(trip,i);
+        cout << temp << endl;
+        delete [] temp; // point to temporary storage
+    }
+    // cin.get();
+    return 0;
+
+}
+
+// This function returns the first ct digits of the number num.
+unsigned long left(unsigned long num, unsigned ct)
+{
+    unsigned digits = 1;
+    unsigned long n = num;
+
+    if (ct == 0 || num == 0)
+        return 0;       // return 0 if no digits
+    while (n /= 10)
+        digits++;
+    if (digits > ct)
+    {
+    ct = digits - ct;
+    while (ct--)
+        num /= 10;
+    return num;         // return left ct digits
+    }
+    else                // if ct >= number of digits
+        return num;     // return the whole number
+}
+
+// This function returns a pointer to a new string
+// consisting of the first n characters in the str string.
+char * left(const char * str, int n)
+{
+    if(n < 0)
+        n = 0;
+    char * p = new char[n+1];
+    int i;
+    for (i = 0; i < n && str[i]; i++)
+        p[i] = str[i];  // copy characters
+    while (i <= n)
+        p[i++] = '\0';  // set rest of string to '\0'
+    return p; 
+}

source/chapter08/secref.cpp

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+// secref.cpp -- defining and using a reference
+#include <iostream>
+int main()
+{
+    using namespace std;
+    int rats = 101;
+    int & rodents = rats;   // rodents is a reference
+
+    cout << "rats = " << rats;
+    cout << ", rodents = " << rodents << endl;
+
+    cout << "rats address = " << &rats;
+    cout << ", rodents address = " << &rodents << endl;
+
+    int bunnies = 50;
+    rodents = bunnies;       // can we change the reference?
+    cout << "bunnies = " << bunnies;
+    cout << ", rats = " << rats;
+    cout << ", rodents = " << rodents << endl;
+
+    cout << "bunnies address = " << &bunnies;
+    cout << ", rodents address = " << &rodents << endl;
+    // cin.get();
+    return 0; 
+}