找不到函数的 C++ 错误标识符？

Question

这是我在 C++ 中的第一步，我正在尝试运行我需要使用的函数

但是我得到这个错误:

Severity Code Description Project File Line Suppression State Error C3861 'findAndRotateBlankNumbers': identifier not found ConsoleApplication2 c:\users\source\repos\consoleapplication2\consoleapplication2\consoleapplication2.cpp 29

这是代码:

//ConsoleApplication2.cpp :定义控制台应用程序的入口点。//

#include "stdafx.h"
#include <iostream>
#include <conio.h>
#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>

enum States {
    needBlank,
    needNumber,
    collectNumbers,
};

bool finish = false;
int i = 0;

int main()

{


    char data[] = { "they're 2fast 96 345 6789 a11 24x 2424" };


    printf(data);
    findAndRotateBlankNumbers(data);
    printf(data);

    system("pause");





    return 0;
}


void findAndRotateBlankNumbers(char* ptr) {
    char* first;
    char* last;
    for (uint8_t state = needBlank; *ptr; ptr++) {
        switch (state) {
        case needBlank:
            if (*ptr == ' ') {
                state = needNumber;
            }
            break;
        case needNumber:
            if (isdigit(*ptr)) {
                state = collectNumbers;
                first = ptr;
            }
            else if (*ptr != ' ') {
                state = needBlank;
            }
            break;
        case collectNumbers:
        {
            bool swap = false;
            if (!isdigit(*ptr)) {
                last = ptr - 1;
                state = (*ptr == ' ' ? needNumber : needBlank);
                swap = true;
            }
            else if (!ptr[1]) {
                last = ptr;
                swap = true;
            }
            if (swap) {
                if (last != first) {
                    for (int8_t nums = (last - first + 1) / 2; nums--; ) {
                        char swap = *first;
                        *first++ = *last;
                        *last-- = swap;
                    }
                }
            }
            break;
        }
        }
    }

}

这是什么？

---

我已经按照您的建议更改了代码的顺序:

#include "stdafx.h"
#include <iostream>
#include <conio.h>
#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>

enum States {
    needBlank,
    needNumber,
    collectNumbers,
};

bool finish = false;
int i = 0;

void findAndRotateBlankNumbers(char* ptr) {
    char* first;
    char* last;
    for (uint8_t state = needBlank; *ptr; ptr++) {
        switch (state) {
        case needBlank:
            if (*ptr == ' ') {
                state = needNumber;
            }
            break;
        case needNumber:
            if (isdigit(*ptr)) {
                state = collectNumbers;
                first = ptr;
            }
            else if (*ptr != ' ') {
                state = needBlank;
            }
            break;
        case collectNumbers:
        {
            bool swap = false;
            if (!isdigit(*ptr)) {
                last = ptr - 1;
                state = (*ptr == ' ' ? needNumber : needBlank);
                swap = true;
            }
            else if (!ptr[1]) {
                last = ptr;
                swap = true;
            }
            if (swap) {
                if (last != first) {
                    for (int8_t nums = (last - first + 1) / 2; nums--; ) {
                        char swap = *first;
                        *first++ = *last;
                        *last-- = swap;
                    }
                }
            }
            break;
        }
        }
    }

}

int main()

{


    char data[] = { "they're 2fast 96 345 6789 a11 24x 2424" };


    printf(data);
    findAndRotateBlankNumbers(data);
    printf(data);

    system("pause");





    return 0;
}

但现在我得到了其他错误:

Severity Code Description Project File Line Suppression State Error C4703 potentially uninitialized local pointer variable 'first' used ConsoleApplication2 c:\users\source\repos\consoleapplication2\consoleapplication2\consoleapplication2.cpp 52

?

Answer 1

您的函数 findAndRotateBlankNumbers 是在您要在 main 中调用它的之后定义的。所以编译器在编译main函数的时候并不知道这个函数的存在。要解决此问题，您可以

• 将 findAndRotateBlankNumbers 函数移到上方 main
• 在顶部添加函数声明并将定义保留在原处:void findAndRotateBlankNumbers(char* ptr);

关于你的第二个错误:

编译器提示您声明变量 first 而没有在初始化时为其赋值。你应该给它一个合理的默认值，比如 char* first = nullptr;

同 char* last = nullptr;

如果您的编译器不支持nullptr，请改用NULL；