将字符串传递给函数以输出它（C++）[关闭]

Posted 2023-02-22

【中文标题】将字符串传递给函数以输出它（C++）[关闭]

【英文标题】：Passing a string to a function to output it (C++) [closed]

【发布时间】：2016-06-07 00:59:02

【问题描述】：

“用 C++ 编写一些东西以在汇编中为微处理器创建方波。 反正我的布局如下：

#include <iostream>
#include <fstream>
#include <string> 

using namespace std;




void code_calc(float cyc, float cyc_high, float cyc_low, string prt, string pncnf, string pnhgh, char prtlttr) 
    ofstream outfile("sqrwv.txt");
    if (outfile.is_open()) 
        cout << "\n\nWriting to file...\n\n"<<prt<<pncnf<<cyc_low;
        outfile << "Sqrwv   MOVLW   0x02            ; Crude count variable\n"
                <<  "   MOVWF   count4          ; Store in COUNT4 to generate wait of 0.5s\n"
                <<  "   BSF STATUS, RP0     ;\n"
                <<  "   BCF STATUS, RP1     ; Select bank 1\n"
                <<  "   MOVLW   B'"<<pncnf<<"'      ; Write / output only on pin 1\n"
                <<  "   MOVWF   TRIS"<<prtlttr<< "          ; so portb is now(wwww wwww)\n"
                <<  "sqhigh BCF STATUS, RP0     ;\n"
                <<  "   BCF STATUS, RP1     ; Select bank 0\n"
                <<  "   BSF "<<prt<<", "<<pnhgh<<"      ; Set pin 1 of port B high\n"
                <<  "   CALL    Delay           ; Wait 0.1s\n"
                <<  "   DECFSZ  count4, 1       ; Decrement COUNT4 to generate\n"
                <<  "   GOTO    sqhigh          ; a flat high signal of 0.5s\n"
                <<  "   MOVLW   0x02            ; Crude count variable again\n"
                <<  "   MOVWF   count5          ; \n"
                <<  "sqlow  NOP             ; NOP to ensure correct cycles on high and low\n"
                <<  "   NOP             ; mirroring the BCFs in HIGH\n"
                <<  "   BCF "<<prt<<", "<<pnhgh<<"      ; Set pin 1 of port B low\n"
                <<  "   NOP             ;\n"
                <<  "   NOP             ;\n"
                <<  "   NOP             ; 93 cycles low\n"
                <<  "   CALL    Delay           ; Wait 0.1s\n"
                <<  "   DECFSZ  count5, 1       ; Decrement COUNT4 to generate a flat low signal\n"
                <<  "   GOTO    sqlow           ; Repeat 4 more times, giving 0.5s\n"
                <<  "   GOTO    Sqrwv           ; If count4 is now zero, just go back to high - forever 83 counts\n";
        outfile.close();
     
    else cout << "Couldn't open file. Try again.";


// outputs menu text when called 
void menu_bs() 
    cout << "       ::::::::::::::::::::::::::::::::::::::::::\n"
        << "        :: Square Wave Generator with Assembly ::\n"        // initiate the menu
        << "        ::::::::::::::::::::::::::::::::::::::::::\n\n"
        << "Follow the instructions in the list, "
        << "and check for output in sqrwv.txt\n\n"
        << "1.  Some important information\n"
        << "2.  Enter your clock speed\n"           // give the user various options
        << "3.  Enter your wave period\n"
        << "4.  Or Enter your wave frequency\n"
        << "5.  Configure your port and pins\n"
        << "6.  Enter your duty cycle\n"
        << "7.  Generate your code\n"
        << "8.  Exit\n\n"           // allow the user to exit using the
        << "Choice: \n";            



void menu() 
    while (1) 
        system("CLS");                  
        char select[1];                         // use as menu select variable 
        menu_bs();
        unsigned long long int speed;
        float time;
        float cycle;
        float cycle_high;
        float cycle_low;
        float period;
        float frequency;
        float duty;
        char portletter;
        string port;
        string pinconf;
        string pinhigh;
        cin >> select;
        if (select[0] == '1')
        
            system("CLS");
            cin.ignore();
            cout << "There are a few things that you should note: \n"
                << "- Designed for use with P16F877A\n"
                << "- You can enter a delay time of 3.4e +/- 38\n"
                << "- For cycle counts <=1277, you only need to reserve for count1\n"
                << "- For cycle counts <=261125, you need to reserve both count1 and count2\n"
                << "- For cycle counts <=62620865, you need to reserve count1, count2 and count3\n"
                << "- The upper cycle limit for the code created is 62620861 cycles\n"
                << "    - This would give a delay of about 62 seconds on a 1MHz clock\n";
            system("PAUSE");
            system("CLS");
        
        if (select[0] == '2')
        
            system("CLS");
            cout << "Your clock speed\n\n";
            cout << "Enter your clock speed in integer form: e.g. 5000000\n\n";
            cin >> speed;
            cout << "\n\nYou chose " << speed << "\n\n";
            system("PAUSE");
            system("CLS");
        

        else if (select[0] == '3')
        
            system("CLS");
            cout << "Your wave period\n\n";
            cout << "Enter your wave period in decimal form or integer: 3.5\n\n";
            cin >> time;
            cout << "\n\n";
            cycle = time * speed;
            cout << "\n\nYou chose a period of " << time << "s\n\n";
            cout << "This corresponds to " << cycle << " cycles for one period.\n\n";
            system("PAUSE");
            system("CLS");
        
        else if (select[0] == '4')
        
            system("CLS");
            cout << "Your wave frequency\n\n";
            cout << "Enter your wave frequency in decmial form or integer: 0.2\n\n";
            cin >> time;
            cout << "\n\n";
            cycle = speed / time;
            cout << "\n\nYou chose a frequency of " << time << "Hz\n\n";
            cout << "This corresponds to " << cycle << " cycles for your frequency\n\n";
            system("PAUSE");
            system("CLS");
        
        else if (select[0] == '5')
        
            system("CLS");
            cout << "Your port configuration\n\n";
            cout << "Enter one port which you'd like to mess with: e.g. PORTA, PORTB, PORTC\n\n";
            cin.ignore();
            getline(cin, port);
            cout << "\n\n";
            cout << "Now enter the write read configuration of the pins on your port: \n e.g. 00000000 = write all, 00001111 = write four, read 4\n\n";
            getline(cin, pinconf);
            cout << "\n\n";
            cout << "Now enter the pin you'd like to toggle high/low: e.g. 1-7\n\n";
            getline(cin, pinhigh);
            pinhigh = pinhigh;
            portletter = port.at(4);
            if (pinconf.length() == 8 && port.length() == 5) 
                cout << "\n\nYou're configured to: " << port << "(" << pinconf << ")\n\n";
                cout << "You'll be using the TRIS" << port.at(4) << " register and will be toggling pin " << pinhigh<<endl<<endl;
             else  cout << "\n\nYour port should be five characters long and your pin \nconfiguration should be eight characters because you have \neight pins. Try again.\n\n";
            system("PAUSE");
            system("CLS");
        
        else if (select[0] == '6')
        
            system("CLS");
            cout << "Your wave duty cycle\n\n";
            cout << "Enter your duty cycle as a decmial (not percentage): e.g. 50% duty cycle = 0.5\n\n";
            cin >> duty;
            cout << "\n\n";
            if (duty >= 1 || duty <= 0) 
                cout << "\n\nYou can't have a duty cycle greater than or less than 100% or 0% respectively.\n\n";
                system("PAUSE");
                system("CLS");
            
            else 
                cycle_high = cycle * duty;
                cycle_low = cycle * (1 - duty);
                cout << "\n\nYou chose a duty cycle of " << duty * 100 << "%\n\n";
                cout << "This corresponds to " << cycle_high << " cycles for your logic high.\n";
                cout << "This corresponds to " << cycle_low << " cycles for your logic low.\n\n";
                system("PAUSE");
                system("CLS");
            
        
        else if (select[0] == '7')
        
            system("CLS");
            cout << cycle << cycle_high << port << pinconf;
            code_calc(cycle, cycle_high, cycle_low, port, pinconf, pinhigh, portletter);
            system("PAUSE");
            system("CLS");
        
        else if (select[0] == '8')                  // quit option
        
            system("CLS");
            exit(0);
            system("PAUSE");
            system("CLS");
        
        else 
                                           
            system("CLS");
            cout << "You have entered an invalid input, please try again.\n";
            cout << "Try to enter a number corresponding to the menu item.\n";
            system("PAUSE");
            system("CLS");
        
    


int main() 
    menu();

如果我在调用a, ... g 变量的先前if 语句之一中调用该函数，则它“排序”有效。但是，我认为因为我在 while 循环的开头启动了变量，所以它们的范围是整个 while 循环，在 if 语句的内部或外部。

所以，目前我的变量没有被传递给我的wv_calc() 函数，因此，我的代码没有内联变量a, b, ..., g。

有什么明显的我做错了吗？

【问题讨论】：

您的问题是关于带有while 循环的代码。你为什么要发布这个函数？

尝试使用更有意义的变量名。我猜你重用了变量。

while 循环代码是不言自明的，我认为有人能够发现变量范围/传递变量的错误，但我现在将发布 while 代码。

wv_calc 甚至不使用您传递的大部分变量。

@Barmar，变量名是为了帖子的简单，我的实际程序中有引用周期数、频率、占空比和周期等的变量名。

【参考方案1】：

查看您的代码，您的很多问题都是由于代码组织不当造成的。

例如，假设您设置了select == 2，您是否看到执行顺序是什么。如下所示，您认为传递给cycle,cycle_high, cycle_low, port and pinconf 的是什么。它们未初始化，因此它们携带的值取决于实现

if (select[0]=='2')
            system("CLS");
            wv_calc(cycle, cycle_high, cycle_low, port, pinconf, pinhigh, portletter);
            system("PAUSE");
            system("CLS");

例如，您的程序的用户必须知道在设置 select = '2' 之前始终设置 select == '1' 以初始化 port, pinconf, pinhigh, portletter。这对您来说可能是显而易见的，但对于以您编写代码的方式生成代码的编译器而言并非如此。

 if (select[0]=='1')
            system("CLS");
            cin.ignore();
            getline(cin, port);
    getline(cin, port);
                getline(cin, pinconf);
                getline(cin, pinhigh);
                portletter = port.at(4);

我也看不到cycle, cycle_high, cycle_low 的值是在哪里设置的。在致电wv_calc之前，它们肯定根本没有设置

更新

这是你需要做的：

void menu() 
    float time;
    float cycle;
    float cycle_high;
    float cycle_low;
    float period;
    float frequency;
    float duty;
    unsigned long long int speed;
    char portletter;
    string port;
    string pinconf;
    string pinhigh;

    while (1) 
        system("CLS");
        //char select[1];       //why do you need an array here
        char select;
        menu_bs();


        cin >> select;
....
....

【讨论】：

"我了解到根据上面的代码循环，cycle_high 和 cycle_low 没有被初始化，但是它们在菜单的其他地方——在其他 if 语句中。"我应该澄清一下，我没有显示初始化它们的代码......但是，每个人似乎都被我的帖子弄糊涂了，我不妨把完整的代码放上来。

我看到了你的问题。您的变量是 while 循环的本地变量。因此，每次重新执行 while 循环时都会重新创建它们。结果，它们以前的值丢失了。检查我更新的答案。顺便说一句，您不能假设用户不会立即跳到选项 7。如果发生这种情况，那么cycle, cycle_high, cycle_low 将是一堆垃圾

选项 2,3,4,5 在您的情况下并不是真正的选项。它们是选项 6 和 7 工作所必需的。尝试重新组织代码。

嘿，Prab，我想它是这样的，谢谢你发现它。该程序仅供我（可能还有其他一些电子工程师）使用，因此输入验证并不是必需的；我知道这是不好的编程习惯，但是没有人会输入 7 并期望可以编译的代码。再次感谢。