錯誤C2371，重新定義； 不同的基本類型

Question

對於函數，我得到錯誤代碼c2371； 分開，最長和最短。 我認為這是關於輸入參數的。

error C2371: 'seperate' : redefinition; different basic types
error C2371: 'shortest' : redefinition; different basic types
error C2371: 'longest' : redefinition; different basic types

碼：

#include <stdio.h>

int main(void)
{
  char msg[41];
  int selector = 0;

  printf("Alinur Caglayan - 18050127622 - Lab Work 5 ");
  printf("Please enter a string message with maximum of 40 characters: ");
  gets(msg);

  printf("Please select one of the following functions:\n1) Longest Word Function");
  printf("\n2) Shortest Word Function\n3) Separate Words Function\n4) Exit: ");
  scanf("%d", &selector);

  if(selector == 1)
  {
    longest(msg);
  }
  else if(selector == 2)
  {
    shortest();
  }
  else if(selector == 3)
  {
    seperate();
  }
  else if(selector == 4)
  {
    return 0;
  }
  else
  {
    printf("\nPlease enter a valid integer!\n");
    scanf("%d", selector);
  }
}

char longest(msg)
{
  char *temp = msg, *word = msg, *max = msg;
  int increment = 0, incrementmax = 0;

  do {
    if(!(*temp & ~32)) 
    {
      if(increment > incrementmax) 
      {
        incrementmax = increment;
        max = word;
      }
      increment = 0;
    } 
    else if(!increment++) 
    {
      word = temp;
    }
  } 
  while(*temp++ != 0);

  for(temp = max; (*temp & ~32); ) 
  {
    printf("%c", *temp++);
  }
}

char shortest(msg)
{
  char *temp = msg, *word = msg, *max = msg;
  int increment = 0, incrementmax = 0;

  do {

    if(!(*temp & ~32)) 
    {

      if(increment > incrementmax) 
      {
        incrementmax = increment;
        max = word;
      }
      increment = 0;
    } 
    else if(!increment++)
    {
      word = temp; 
    }
  } 
  while(*temp++ != 0);

  for(temp = max; (*temp & ~32); ) 
  {
    printf("%c", *temp++);
  }
}

char seperate(msg)
{

  char *temp = msg;
  int i;

  printf("Alinur Caglayan - 18050127622 - Lab Work 5 ");
  printf("Please enter a string message with maximum of 40 characters: ");
  gets(msg);

  for(i=0; i < 41; i++)
  {
    if(*temp & ~32)
    {
      printf("\n");
    }
    else
    {
      printf("%c", temp);
    }
    system("pause");
  }
}

Answer 1

您在調用函數時沒有先聲明它們的類型。 這兩個最新版本的C標准不允許這樣做，並且應導致產生診斷消息。

但是，如果您的編譯器符合較舊的標准（或完全沒有），則調用未聲明的函數將導致編譯器提供其自己的聲明，其返回類型默認為int 。 以后將函數定義為具有不同的返回類型時，編譯器會警告您不匹配。

您應該始終聲明函數（即返回類型及其參數的類型）， 或者在瑣碎的情況下，在調用函數之前先定義函數（即具有函數體）。

Answer 2

有很多錯誤。

您應該在main之前聲明函數，如下所示：

char shortest(char msg[41]);
char longest(char msg[41]);

或者如果您不想聲明它們，可以在main之前定義它們。

您也有：

scanf("%d", selector);

雖然應該是：

scanf("%d", &selector);

並且您的所有functioncs也應該返回一個char。

編輯：另一件事是您定義函數，例如：

char longest(msg) {
    ...
}

但是您必須像這樣指定參數的類型。

char longest(char msg[41]) {
    ...
}

Answer 3

以下內容僅糾正了基本語法，而沒有研究子功能的實際作用：

#include <stdio.h>
#include <stdlib.h>

// prototypes
void longest ( char * );
void shortest( char * );
void seperate( char * );

int main(void)
{
    char msg[41];
    int selector = 0;

    printf("Alinur Caglayan - 18050127622 - Lab Work 5 ");
    printf("Please enter a string message with maximum of 40 characters: ");
    if( NULL == fgets(msg, sizeof(msg), stdin) )
    {
        perror( "fgets failed" );
        exit( EXIT_FAILURE );
    }

    int done = 0; // indicate not done

    while(!done)
    { 
        printf("Please select one of the following functions:\n");
        printf( "1) Longest Word Function\n");
        printf( "2) Shortest Word Function\n");
        printf( "3) Separate Words Function\n");
        printf( "4) Exit:\n");

        if( 1 != scanf(" %d", &selector) )
        {
            perror( "scanf failed" );
            exit( EXIT_FAILURE );
        } 

        switch( selector )
        {
            case 1:
                longest(msg);
                break;

            case 2:
                shortest(msg);
                break;

            case 3:
                seperate(msg);
                break;

            case 4:
                done = 1; // cause loop to exit
                break;

            default:
                printf("\nERROR: invalid selection entered\n");
                break;
        } // end switch
    } // end while

    return(0);
} // end funtion: main


void longest( char* msg)
{
    char *temp = msg, *word = msg, *max = msg;
    int increment = 0, incrementmax = 0;

    do {
        if(!(*temp & ~32)) 
        {
            if(increment > incrementmax) 
            {
                incrementmax = increment;
                max = word;
            } // end if

            increment = 0;
        }

        else if(!increment++) 
        {
            word = temp;
        } // end if
    } while(*temp++ != 0);

    for(temp = max; (*temp & ~32); ) 
    {
    printf("%c", *temp++);
    }
} // end function: longest

void shortest(char* msg)
{
    char *temp = msg, *word = msg, *max = msg;
    int increment = 0, incrementmax = 0;

    do {

        if(!(*temp & ~32)) 
        {

            if(increment > incrementmax) 
            {
                incrementmax = increment;
                max = word;
            } // end if
            increment = 0;
        }

        else if(!increment++)
        {
            word = temp; 
        }
    } while(*temp++ != 0);

    for(temp = max; (*temp & ~32); temp++) 
    {
        printf("%c", *temp);
    }
} // end function: shortest

void seperate(char* msg)
{

    char *temp = msg;
    int i;

    printf("Alinur Caglayan - 18050127622 - Lab Work 5 ");
    printf("Please enter a string message with maximum of 40 characters: ");
    if( NULL == fgets(msg, sizeof(msg), stdin) )
    {
        perror( "fgets failed" );
        exit( EXIT_FAILURE );
    }

    for(i=0; i < 41; i++)
    {
        if(*temp & ~32)
        {
            printf("\n");
        }
        else
        {
            printf("%c", temp);
        }  // end if

        system("pause");
    } // end for
} // end function: seperate