为什么我的打印功能会输出垃圾，而我当前的功能无法正常工作？

Question

这是头文件 http://pastebin.com/g0z7LkeN 这是实现文件 http://pastebin.com/USHbjbYC

这是测试调试器文件（不应该更改它）

// FILE: sequence_test.cpp
// An interactive test program for the new sequence class
#include <cctype>       // Provides toupper
#include <iostream>     // Provides cout and cin
#include <cstdlib>      // Provides EXIT_SUCCESS
#include "sequence2.h"  // With value_type defined as double
using namespace std;
using namespace CISP430_A2;

// PROTOTYPES for functions used by this test program:
void print_menu( );
// Postcondition: A menu of choices for this program has been written to cout.

char get_user_command( );
// Postcondition: The user has been prompted to enter a one character command.
// The next character has been read (skipping blanks and newline characters), 
// and this character has been returned.

void show_sequence(sequence display);
// Postcondition: The items on display have been printed to cout (one per line).

double get_number( );
// Postcondition: The user has been prompted to enter a real number. The
// number has been read, echoed to the screen, and returned by the function.


int main( )
{
    sequence test; // A sequence that we’ll perform tests on
    char choice;   // A command character entered by the user

    cout << "I have initialized an empty sequence of real numbers." << endl;

    do
    {
        print_menu( );
        choice = toupper(get_user_command( ));
        switch (choice)
        {
            case '!': test.start( );
                      break;
            case '+': test.advance( );
                      break;
            case '?': if (test.is_item( ))
                          cout << "There is an item." << endl;
                      else 
                          cout << "There is no current item." << endl;
                      break;
            case 'C': if (test.is_item( ))
                           cout << "Current item is: " << test.current( ) << endl;
                      else
                          cout << "There is no current item." << endl;
                      break;
            case 'P': show_sequence(test);
                      break;
            case 'S': cout << "Size is " << test.size( ) << '.' << endl;
                      break;
            case 'I': test.insert(get_number( ));
                      break;
            case 'A': test.attach(get_number( ));
                      break;
            case 'R': test.remove_current( );
                      cout << "The current item has been removed." << endl;
                      break;     
            case 'Q': cout << "Ridicule is the best test of truth." << endl;
                      break;
            default:  cout << choice << " is invalid." << endl;
        }
    }
    while ((choice != 'Q'));

    return EXIT_SUCCESS;
}

void print_menu( )
// Library facilities used: iostream.h
{
    cout << endl; // Print blank line before the menu
    cout << "The following choices are available: " << endl;
    cout << " !   Activate the start( ) function" << endl;
    cout << " +   Activate the advance( ) function" << endl;
    cout << " ?   Print the result from the is_item( ) function" << endl;
    cout << " C   Print the result from the current( ) function" << endl;
    cout << " P   Print a copy of the entire sequence" << endl;
    cout << " S   Print the result from the size( ) function" << endl;
    cout << " I   Insert a new number with the insert(...) function" << endl;
    cout << " A   Attach a new number with the attach(...) function" << endl;
    cout << " R   Activate the remove_current( ) function" << endl;
    cout << " Q   Quit this test program" << endl;
}

char get_user_command( )
// Library facilities used: iostream
{
    char command;

    cout << "Enter choice: ";
    cin >> command; // Input of characters skips blanks and newline character

    return command;
}

void show_sequence(sequence display)
// Library facilities used: iostream
{
    for (display.start( ); display.is_item( ); display.advance( ))
        cout << display.current( ) << endl;
}

double get_number( )
// Library facilities used: iostream
{
    double result;

    cout << "Please enter a real number for the sequence: ";
    cin  >> result;
    cout << result << " has been read." << endl;
    return result;
}

当我在调试器中单击选项 P 打印整个序列时，它永远无法正常工作并且经常吐出垃圾，当我在插入或附加 2 个数字后单击调试器菜单中的 c 时，它似乎不正常也可以正常工作。我分析了我的算法，但我不明白为什么它们不能正常工作。

Answer 1

摘要：

您正在使用默认构造函数创建类序列的实例，该构造函数不会分配存储数字的数组，这将在从菜单调用任何函数时导致不正确的行为因为它们依赖于要正确初始化的数组。您需要做的是使用另一个构造函数（即采用大小参数的构造函数）创建测试实例。

原文

通过查看上面的“测试调试器文件”，我注意到您调用了类序列的默认构造函数：

sequence test; // A sequence that we’ll perform tests on

查看实现，我找不到已实现它的地方。我认为构造函数：

sequence(size_type entry=CAPACITY )

是您需要调用的，以便“新”底层数组数据并在启动时正确设置索引。例如，当前代码将在调用 show_sequence(test) 时从未初始化的随机内存中读取数据。