第八章：指针06
让编程改动国际
Change the world by program
字符指针作函数参数
出错了：关于a[]和*a的一些差异！
include
void??main()
{
? ?? ?void copy_string( char from, char to );
? ?? ?char *a = "I am a teacher.";
? ?? ?char b[] = "You are a student."; //此处应该界说为char b[] = "You are a student.";
? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?//差异两者反汇编代码并解说其含义
? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?//谈谈五个区!
? ?? ?printf("String a = %snString b = %sn", a, b);
? ?? ?printf("copy string a to string b:n");
? ?? ?copy_string(a, b);
? ?? ?printf("nString a = %snString b = %sn", a, b);
}
void??copy_string( char from, char to )
{
? ?? ?for( ; *from != '?'; from++,to++)
? ?? ?{
? ?? ?? ?? ?to = from;
? ?? ?}
? ?? ?*to = '?';
}
优化：对 copy_string 函数还可作简化
办法一
include
void??main()
{
? ?? ?void copy_string( char from, char to );
? ?? ?char *a = "I am a teacher.";
? ?? ?char b[] = "You are a student.";
? ?? ?printf("String a = %snString b = %sn", a, b);
? ?? ?printf("copy string a to string b:n");
? ?? ?copy_string(a, b);
? ?? ?printf("nString a = %snString b = %sn", a, b);
}
void??copy_string( char from, char to )
{
? ?? ?while( (to = from) != '?' )
? ?? ?{
? ?? ?? ?? ?to++;
? ?? ?? ?? ?from++;
? ?? ?}
}
办法二
include
void??main()
{
? ?? ?void copy_string( char from, char to );
? ?? ?char *a = "I am a teacher.";
? ?? ?char b[] = "You are a student.";
? ?? ?printf("String a = %snString b = %sn", a, b);
? ?? ?printf("copy string a to string b:n");
? ?? ?copy_string(a, b);
? ?? ?printf("nString a = %snString b = %sn", a, b);
}
void??copy_string( char from, char to )
{
? ?? ?while( (to++ = from++) != '?')
? ?? ?{
? ?? ?? ?? ?;
? ?? ?}
}
办法三
include
void??main()
{
? ?? ?void copy_string( char from, char to );
? ?? ?char *a = "I am a teacher.";
? ?? ?char b[] = "You are a student.";
? ?? ?printf("String a = %snString b = %sn", a, b);
? ?? ?printf("copy string a to string b:n");
? ?? ?copy_string(a, b);
? ?? ?printf("nString a = %snString b = %sn", a, b);
}
void??copy_string( char from, char to )
{
? ?? ?while( *from != '?' )
? ?? ?{
? ?? ?? ?? ?to++ = from++;
? ?? ?}
? ?? ?*to = '?';
}
办法四
include
void??main()
{
? ?? ?void copy_string( char from, char to );
? ?? ?char *a = "I am a teacher.";
? ?? ?char b[] = "You are a student.";
? ?? ?printf("String a = %snString b = %sn", a, b);
? ?? ?printf("copy string a to string b:n");
? ?? ?copy_string(a, b);
? ?? ?printf("nString a = %snString b = %sn", a, b);
}
void??copy_string( char from, char to )
{
? ?? ?while( to++ = from++ )
? ?? ?{
? ?? ?? ?? ?;? ? // '?' == 0
? ?? ?}
}
办法五
include
void??main()
{
? ?? ?void copy_string( char from, char to );
? ?? ?char *a = "I am a teacher.";
? ?? ?char b[] = "You are a student.";
? ?? ?printf("String a = %snString b = %sn", a, b);
? ?? ?printf("copy string a to string b:n");
? ?? ?copy_string(a, b);
? ?? ?printf("nString a = %snString b = %sn", a, b);
}
void??copy_string( char from, char to )
{
? ?? ?for( ; to++ = from++; )
? ?? ?{
? ?? ?? ?? ?;
? ?? ?}
}
办法六
include
void??main()
{
? ?? ?void copy_string( char from, char to );
? ?? ?char *a = "I am a teacher.";
? ?? ?char b[] = "You are a student.";
? ?? ?printf("String a = %snString b = %sn", a, b);
? ?? ?printf("copy string a to string b:n");
? ?? ?copy_string(a, b);
? ?? ?printf("nString a = %snString b = %sn", a, b);
}
void??copy_string( char from[], char to[] )
{
? ?? ?char p1, p2;
? ?? ?p1 = from;
? ?? ?p2 = to;
? ?? ?while( (p2++ = p1++) != '?' )
? ?? ?{
? ?? ?? ?? ?;
? ?? ?}
}
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