提交chapter07

source/chapter07/arfupt.cpp

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+// arfupt.cpp -- an array of function pointers
+#include <iostream>
+// various notations, same signatures
+const double * f1(const double ar[], int n);
+const double * f2(const double [], int);
+const double * f3(const double *, int);
+
+int main()
+{
+    using namespace std;
+    double av[3] = {1112.3, 1542.6, 2227.9};
+
+    // pointer to a function
+    const double *(*p1)(const double *, int) = f1;
+    auto p2 = f2;  // C++0x automatic type deduction
+    // pre-C++0x can use the following code instead
+    // const double *(*p2)(const double *, int) = f2;
+     cout << "Using pointers to functions:\n";
+    cout << " Address  Value\n";
+    cout <<  (*p1)(av,3) << ": " << *(*p1)(av,3) << endl;
+    cout << p2(av,3) << ": " << *p2(av,3) << endl;
+
+    // pa an array of pointers
+    // auto doesn't work with list initialization
+    const double *(*pa[3])(const double *, int) = {f1,f2,f3};
+    // but it does work for initializing to a single value
+    // pb a pointer to first element of pa
+    auto pb = pa;
+    // pre-C++0x can use the following code instead
+    // const double *(**pb)(const double *, int) = pa;
+    cout << "\nUsing an array of pointers to functions:\n";
+    cout << " Address  Value\n";
+    for (int i = 0; i < 3; i++)
+        cout << pa[i](av,3) << ": " << *pa[i](av,3) << endl;
+    cout << "\nUsing a pointer to a pointer to a function:\n";
+    cout << " Address  Value\n";
+    for (int i = 0; i < 3; i++)
+        cout << pb[i](av,3) << ": " << *pb[i](av,3) << endl;
+
+    // what about a pointer to an array of function pointers
+    cout << "\nUsing pointers to an array of pointers:\n";
+    cout << " Address  Value\n";
+    // easy way to declare pc 
+    auto pc = &pa; 
+     // pre-C++0x can use the following code instead
+    // const double *(*(*pc)[3])(const double *, int) = &pa;
+   cout << (*pc)[0](av,3) << ": " << *(*pc)[0](av,3) << endl;
+    // hard way to declare pd
+    const double *(*(*pd)[3])(const double *, int) = &pa;
+    // store return value in pdb
+    const double * pdb = (*pd)[1](av,3);
+    cout << pdb << ": " << *pdb << endl;
+    // alternative notation
+    cout << (*(*pd)[2])(av,3) << ": " << *(*(*pd)[2])(av,3) << endl;
+    // cin.get();
+    return 0;
+}
+
+// some rather dull functions
+
+const double * f1(const double * ar, int n)
+{
+    return ar;
+}
+const double * f2(const double ar[], int n)
+{
+    return ar+1;
+}
+const double * f3(const double ar[], int n)
+{
+    return ar+2;
+}

source/chapter07/arfupt1.cpp

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+// arfupt.cpp -- an array of function pointers
+#include <iostream>
+// various notations, same signatures
+const double * f1(const double ar[], int n);
+const double * f2(const double [], int);
+const double * f3(const double *, int);
+
+int main()
+{
+    using namespace std;
+    double av[3] = {1112.3, 1542.6, 2227.9};
+
+    // pointer to a function
+    typedef const double *(*p_fun)(const double *, int);
+    p_fun p1 = f1;
+    auto p2 = f2;  // C++0x automatic type deduction
+    cout << "Using pointers to functions:\n";
+    cout << " Address  Value\n";
+    cout <<  (*p1)(av,3) << ": " << *(*p1)(av,3) << endl;
+    cout << p2(av,3) << ": " << *p2(av,3) << endl;
+
+    // pa an array of pointers
+     p_fun pa[3] = {f1,f2,f3};
+    // auto doesn't work with list initialization
+    // but it does work for initializing to a single value
+    // pb a pointer to first element of pa
+    auto pb = pa;
+    cout << "\nUsing an array of pointers to functions:\n";
+    cout << " Address  Value\n";
+    for (int i = 0; i < 3; i++)
+        cout << pa[i](av,3) << ": " << *pa[i](av,3) << endl;
+    cout << "\nUsing a pointer to a pointer to a function:\n";
+    cout << " Address  Value\n";
+    for (int i = 0; i < 3; i++)
+        cout << pb[i](av,3) << ": " << *pb[i](av,3) << endl;
+
+    // what about a pointer to an array of function pointers
+    cout << "\nUsing pointers to an array of pointers:\n";
+    cout << " Address  Value\n";
+    // easy way to declare pc 
+    auto pc = &pa; 
+    cout << (*pc)[0](av,3) << ": " << *(*pc)[0](av,3) << endl;
+    // slightly harder way to declare pd
+	p_fun (*pd)[3] = &pa;
+    // store return value in pdb
+    const double * pdb = (*pd)[1](av,3);
+    cout << pdb << ": " << *pdb << endl;
+    // alternative notation
+    cout << (*(*pd)[2])(av,3) << ": " << *(*(*pd)[2])(av,3) << endl;
+    // cin.get();
+    return 0;
+}
+
+// some rather dull functions
+
+const double * f1(const double * ar, int n)
+{
+    return ar;
+}
+const double * f2(const double ar[], int n)
+{
+    return ar+1;
+}
+const double * f3(const double ar[], int n)
+{
+    return ar+2;
+}

source/chapter07/arrfun1.cpp

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+// arrfun1.cpp -- functions with an array argument
+#include <iostream>
+const int ArSize = 8;
+int sum_arr(int arr[], int n);        // prototype
+int main()
+{
+    using namespace std;
+    int cookies[ArSize] = {1,2,4,8,16,32,64,128};
+// some systems require preceding int with static to
+// enable array initialization
+
+    int sum = sum_arr(cookies, ArSize);
+    cout << "Total cookies eaten: " << sum <<  "\n";
+    // cin.get();
+    return 0;
+}
+
+// return the sum of an integer array
+int sum_arr(int arr[], int n)
+{
+    int total = 0;
+
+    for (int i = 0; i < n; i++)
+        total = total + arr[i];
+    return total; 
+}

source/chapter07/arrfun2.cpp

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+// arrfun2.cpp -- functions with an array argument
+#include <iostream>
+const int ArSize = 8;
+int sum_arr(int arr[], int n);
+// use std:: instead of using directive
+int main()
+{
+    int cookies[ArSize] = {1,2,4,8,16,32,64,128};
+//  some systems require preceding int with static to
+//  enable array initialization
+
+    std::cout << cookies << " = array address, ";
+//  some systems require a type cast: unsigned (cookies)
+
+    std::cout << sizeof cookies << " = sizeof cookies\n";
+    int sum = sum_arr(cookies, ArSize);
+    std::cout << "Total cookies eaten: " << sum <<  std::endl;
+    sum = sum_arr(cookies, 3);        // a lie
+    std::cout << "First three eaters ate " << sum << " cookies.\n";
+    sum = sum_arr(cookies + 4, 4);    // another lie
+    std::cout << "Last four eaters ate " << sum << " cookies.\n";
+    // std::cin.get();
+	return 0;
+}
+
+// return the sum of an integer array
+int sum_arr(int arr[], int n)
+{
+    int total = 0;
+    std::cout << arr << " = arr, ";
+// some systems require a type cast: unsigned (arr)
+
+    std::cout << sizeof arr << " = sizeof arr\n";
+    for (int i = 0; i < n; i++)
+        total = total + arr[i];
+    return total; 
+}

source/chapter07/arrfun3.cpp

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+// arrfun3.cpp -- array functions and const
+#include <iostream>
+const int Max = 5;
+
+// function prototypes
+int fill_array(double ar[], int limit);
+void show_array(const double ar[], int n);  // don't change data
+void revalue(double r, double ar[], int n);
+
+int main()
+{
+    using namespace std;
+    double properties[Max];
+
+    int size = fill_array(properties, Max);
+    show_array(properties, size);
+    if (size > 0)
+    {
+        cout << "Enter revaluation factor: ";
+        double factor;
+        while (!(cin >> factor))    // bad input
+        {
+            cin.clear();
+            while (cin.get() != '\n')
+                continue;
+           cout << "Bad input; Please enter a number: ";
+        }
+        revalue(factor, properties, size);
+        show_array(properties, size);
+    }
+    cout << "Done.\n";
+    // cin.get();
+    // cin.get();
+    return 0;
+}
+
+int fill_array(double ar[], int limit)
+{
+    using namespace std;
+    double temp;
+    int i;
+    for (i = 0; i < limit; i++)
+    {
+        cout << "Enter value #" << (i + 1) << ": ";
+        cin >> temp;
+        if (!cin)    // bad input
+        {
+            cin.clear();
+            while (cin.get() != '\n')
+                continue;
+           cout << "Bad input; input process terminated.\n";
+           break;
+        }
+        else if (temp < 0)     // signal to terminate
+            break;
+        ar[i] = temp;
+    }
+    return i;
+}
+
+// the following function can use, but not alter,
+// the array whose address is ar
+void show_array(const double ar[], int n)
+{
+    using namespace std;
+    for (int i = 0; i < n; i++)
+    {
+        cout << "Property #" << (i + 1) << ": $";
+        cout << ar[i] << endl;
+    }
+}
+
+// multiplies each element of ar[] by r
+void revalue(double r, double ar[], int n)
+{
+    for (int i = 0; i < n; i++)
+        ar[i] *= r;
+}

source/chapter07/arrfun4.cpp

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+// arrfun4.cpp -- functions with an array range
+#include <iostream>
+const int ArSize = 8;
+int sum_arr(const int * begin, const int * end);
+int main()
+{
+    using namespace std;
+    int cookies[ArSize] = {1,2,4,8,16,32,64,128};
+//  some systems require preceding int with static to
+//  enable array initialization
+
+    int sum = sum_arr(cookies, cookies + ArSize);
+    cout << "Total cookies eaten: " << sum <<  endl;
+    sum = sum_arr(cookies, cookies + 3);        // first 3 elements
+    cout << "First three eaters ate " << sum << " cookies.\n";
+    sum = sum_arr(cookies + 4, cookies + 8);    // last 4 elements
+    cout << "Last four eaters ate " << sum << " cookies.\n";
+    // cin.get();
+    return 0;
+}
+
+// return the sum of an integer array
+int sum_arr(const int * begin, const int * end)
+{
+    const int * pt;
+    int total = 0;
+
+    for (pt = begin; pt != end; pt++)
+        total = total + *pt;
+    return total; 
+}

source/chapter07/arrobj.cpp

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+//arrobj.cpp -- functions with array objects
+#include <iostream>
+#include <array>
+#include <string>
+const int Seasons = 4;
+const std::array<std::string, Seasons> Snames =
+    {"Spring", "Summer", "Fall", "Winter"};
+
+void fill(std::array<double, Seasons> * pa);
+void show(std::array<double, Seasons> da);
+int main()
+{
+    std::array<double, 4> expenses;
+    fill(&expenses);
+    show(expenses);
+    // std::cin.get();
+    // std::cin.get();
+    return 0;
+}
+
+void fill(std::array<double, Seasons> * pa)
+{
+    for (int i = 0; i < Seasons; i++)
+    {
+        std::cout << "Enter " << Snames[i] << " expenses: ";
+        std::cin >> (*pa)[i];
+    }
+}
+
+void show(std::array<double, Seasons> da)
+{
+    double total = 0.0;
+    std::cout << "\nEXPENSES\n";
+    for (int i = 0; i < Seasons; i++)
+    {
+        std::cout << Snames[i] << ": $" << da[i] << '\n';
+        total += da[i];
+    }
+    std::cout << "Total: $" << total << '\n';
+}

source/chapter07/calling.cpp

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+// calling.cpp -- defining, prototyping, and calling a function
+#include <iostream>
+
+void simple();    // function prototype
+
+int main()
+{
+    using namespace std;
+    cout << "main() will call the simple() function:\n";
+    simple();     // function call
+	cout << "main() is finished with the simple() function.\n";
+    // cin.get();
+    return 0;
+}
+
+// function definition
+void simple()
+{
+    using namespace std;
+    cout << "I'm but a simple function.\n";
+}