指针06 - 零基础入门学习C语言46

第八章：指针06

 

让编程改变世界

Change the world by program

---

 

字符指针作函数参数

出错了：关于a[]和*a的一些区别！ [codesyntax lang="c"]

#include <stdio.h>

void  main()
{
      void copy_string( char *from, char *to );

      char *a = "I am a teacher.";
      char b[] = "You are a student."; //此处应该定义为char b[] = "You are a student.";
                                       //区别两者反汇编代码并解释其意义
                                       //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 = '�';
}

[/codesyntax]  

优化：对 copy_string 函数还可作简化

方法一

[codesyntax lang="c"]

#include <stdio.h>

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++;
      }
}

[/codesyntax]

方法二

[codesyntax lang="c"]

#include <stdio.h>

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++) != '�')
      {
            ;
      }
}

[/codesyntax]

方法三

[codesyntax lang="c"]

#include <stdio.h>

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 = '�';
}

[/codesyntax]

方法四

[codesyntax lang="c"]

#include <stdio.h>

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
      }
}

[/codesyntax]

方法五

[codesyntax lang="c"]

#include <stdio.h>

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++; )
      {
            ;
      }
}

[/codesyntax]

方法六

[codesyntax lang="c"]

#include <stdio.h>

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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