char*& and char* ???

[pembed2003]

Hi coders,
I have the following:

void f1(char* &s){
*s = 'a';
}

void f2(char* s){
*s = 'b';
}

int main(int argc,char** argv){
char a[] = "1234";
char* b = a;
printf("%s\n",a );
f1(b);
printf("%s\n",a );
f2(b);
printf("%s\n",a );
return 0;
}

The above prints:

1234
a234
b234

My question is:

1. How is char*& different from char* since they both do the same thing?
2. When do you use the first form and the second form?

Thanks!

[James McIninch]

pembed2003 wrote:

Hi coders,
I have the following:

void f1(char* &s){
*s = 'a';
}

void f2(char* s){
*s = 'b';
}

int main(int argc,char** argv){
char a[] = "1234";
char* b = a;
printf("%s\n",a );
f1(b);
printf("%s\n",a );
f2(b);
printf("%s\n",a );
return 0;
}

The above prints:

1234
a234
b234

My question is:

1. How is char*& different from char* since they both do the same thing?
No. In C, char*& is a syntax error. There is no such syntax in C.

2. When do you use the first form and the second form?
You use char * all the time since the other form doesn't exist.


Thanks!

--
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[Chris Fogelklou]

"pembed2003 " <pe********@yah oo.com> wrote in message
news:db******** *************** ***@posting.goo gle.com...

Hi coders,
I have the following:

void f1(char* &s){
*s = 'a';
}

void f2(char* s){
*s = 'b';
}

int main(int argc,char** argv){
char a[] = "1234";
char* b = a;
printf("%s\n",a );
f1(b);
printf("%s\n",a );
f2(b);
printf("%s\n",a );
return 0;
}

The above prints:

1234
a234
b234

My question is:

1. How is char*& different from char* since they both do the same thing?
2. When do you use the first form and the second form?

Thanks! void f1(char* &s){
As everyone said... this is a syntax error in C.
1. How is char*& different from char* since they both do the same thing?
However, in C++, you are passing a char * by reference... meaning, not only
could you have modified the character pointed to by 's' in the same way, but
the pointer 's' itself:

s = NULL; //This change would be undone by returning if s was not passed by
reference.

So, you must somehow be compiling in C++ rather than C.
2. When do you use the first form and the second form?

In C/C++, use the first form when you don't want to modify the value of the
variable passed in.

You would only use the second form in C++, and only when you want the
changes that you make to the variable to be returned to the calling program.

In C, you can only modify variables passed into a function through pointers:

void f1(char **ps){
*ps = NULL; //Kill s.
}