#include<stdio.h>
#include<string.h>
#include<ctype.h>
#define LEN 81
char* s_gets(char* st, int n);
char showmenu(void);
void eatline(void);
void show(void (*fp)(char*), char* str);
void ToUpper(char*);
void ToLower(char*);
void Transpose(char*);
void Dummy(char*);
int main(void)
{
char line[LEN];
char copy[LEN];
char choice;
void (*pfun)(char*);
puts("Enter a string (empty line to quit:)");
while (s_gets(line, LEN) != NULL && line[0] != '\0')
{
while ((choice = showmenu()) != 'n')
{
switch (choice)
{
case 'u':
pfun = ToUpper;
break;
case 'l':
pfun = ToLower;
break;
case 't':
pfun = Transpose;
break;
case 'o':
pfun = Dummy;
break;
}
strcpy_s(copy,LEN,line);
show(pfun, copy);
}
puts("Enter a string (empty line to quit):");
}
puts("Bye!");
return 0;
}
char showmenu(void)
{
char ans;
puts("Enter menu choice:");
puts("u) uppercase l)lowercase");
puts("t) transposed case o)original case");
puts("n) next string");
ans = getchar();
ans = tolower(ans);
eatline();
while (strchr("ulton", ans) == NULL)
{
puts("Please enter a u,l,t,o, or n:");
ans = tolower(getchar());
eatline();
}
return ans;
}
void eatline(void)
{
while (getchar() != '\n')
continue;
}
void ToUpper(char* str)
{
while (*str)
{
*str = toupper(*str);
str++;
}
}
void ToLower(char* str)
{
while (*str)
{
*str = tolower(*str);
str++;
}
}
void Transpose(char* str)
{
while (*str)
{
if (islower(*str))
*str = toupper(*str);
else if (isupper(*str))
*str = tolower(*str);
str++;
}
}
void Dummy(char* str)
{
}
void show(void(*fp)(char*), char* str)
{
(*fp)(str);
puts(str);
}
char* s_gets(char* st, int n)
{
char* ret_val;
char* find;
ret_val = fgets(st, n, stdin);
if (ret_val)
{
find = strchr(st, '\n');
if (find)
*find = '\0';
else
while (getchar() != '\n')
continue;
}
return ret_val;
}
为什么报错报错43行未初始化局部变量pfun?原因是什么?