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! 11 3517
"pembed2003 " <pe********@yah oo.com> wrote in message 1. How is char*& different from char* since they both do the same > thing?
char *& is C++ and ia a pointer passed by reference. char * is C and is just
a pointer. 2. When do you use the first form and the second form?
First form when programming in C++. You need to ask in clc++ about when it
is appropriate to use references and when to use pointers.
You would use the second form whenever you want to pass an array of
characters (eg a string) to a C function, and in a few other cases.
pembed2003 wrote: Hi coders, I have the following:
void f1(char* &s){
^^^^^^^^
syntax error
[...]
1. How is char*& different from char*
'char*&' is a syntax error, 'char*' isn't.
since they both do the same thing?
No they don't.
2. When do you use the first form
Never
and the second form?
When you need a pointer to char
Martin Ambuhl <ma*****@earthl ink.net> wrote in message news:<c5******* *****@ID-227552.news.uni-berlin.de>... pembed2003 wrote: Hi coders, I have the following:
void f1(char* &s){ ^^^^^^^^ syntax error [...]
I compile the code using gcc but it doesn't produce any error. do you
know why? Is gcc a C compiler? 1. How is char*& different from char* 'char*&' is a syntax error, 'char*' isn't.
since they both do the same thing?
No they don't.
sorry. i mean that they do the same thing in the sample program I
posted. 2. When do you use the first form
Never
Why? and the second form?
When you need a pointer to char
Thanks!
pembed2003 wrote: Martin Ambuhl <ma*****@earthl ink.net> wrote in message news:<c5******* *****@ID-227552.news.uni-berlin.de>...
pembed2003 wrote:
Hi coders, I have the following:
void f1(char* &s){ ^^^^^^^^ syntax error [...]
I compile the code using gcc but it doesn't produce any error. do you know why? Is gcc a C compiler?
You didn't invoke gcc properly.
suppost your program is named a.c
Try one of
gcc -Wall -W -std=c89 -pedantic a.c
gcc -Wall -W -ansi -pedantic a.c
gcc -Wall -W -std=c99 -pedantic a.c
1. How is char*& different from char* 'char*&' is a syntax error, 'char*' isn't.
since they both do the same thing?
No they don't.
sorry. i mean that they do the same thing in the sample program I posted.
They don't do the same thing, period. 'char* &' is a syntax error which
gcc, when properly invoked, is reported as a parsing error. It is
impossible for a syntax error to predictably have the same effect as
legal code. The most likely result of syntax error is a compilation
failure. 2. When do you use the first form
Never
Why?
If you don't get this, you are truly an idiot.
"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'; }
That looks like C++; it's not valid C.
void f2(char* s){ *s = 'b'; }
That is valid C.
S
--
Stephen Sprunk "Stupid people surround themselves with smart
CCIE #3723 people. Smart people surround themselves with
K5SSS smart people who disagree with them." --Aaron Sorkin pe********@yaho o.com (pembed2003) writes: Is gcc a C compiler?
No. GCC stands for "GNU Compiler Collection". The collection currently
includes compilers for C, C++, Objective C, Java, Fortran, and Ada.
Martin
--
,--. Martin Dickopp, Dresden, Germany ,= ,-_-. =.
/ ,- ) http://www.zero-based.org/ ((_/)o o(\_))
\ `-' `-'(. .)`-'
`-. Debian, a variant of the GNU operating system. \_/
In article <db************ **************@ posting.google. com>, pe********@yaho o.com (pembed2003) wrote: Martin Ambuhl <ma*****@earthl ink.net> wrote in message news:<c5******* *****@ID-227552.news.uni-berlin.de>... pembed2003 wrote: Hi coders, I have the following:
void f1(char* &s){ ^^^^^^^^ syntax error [...]
I compile the code using gcc but it doesn't produce any error. do you know why? Is gcc a C compiler?
I should really hope that you know which language your compiler is
compiling. Read the documentation.
Try compiling this:
int main (void)
{
int new = 0;
int class = 0;
return new + class;
}
and see what your compiler thinks about it. pe********@yaho o.com (pembed2003) writes: Martin Ambuhl <ma*****@earthl ink.net> wrote in message news:<c5******* *****@ID-227552.news.uni-berlin.de>... pembed2003 wrote: Hi coders, I have the following:
void f1(char* &s){ ^^^^^^^^ syntax error [...]
I compile the code using gcc but it doesn't produce any error. do you know why? Is gcc a C compiler?
It can be; it can also be a C++ compiler. It typically decides which
frontend to invoke based on the suffix on the file name. If your
source file has a name ending in ".c", gcc should correctly report a
syntax error on the above; if it ends in ".C" or ".cc", it will assume
it's C++, and behave in a manner that we're not qualified to discuss
in this newsgroup.
--
Keith Thompson (The_Other_Keit h) ks***@mib.org <http://www.ghoti.net/~kst>
San Diego Supercomputer Center <*> <http://users.sdsc.edu/~kst>
Schroedinger does Shakespeare: "To be *and* not to be"
In <db************ **************@ posting.google. com> pe********@yaho o.com (pembed2003) writes: 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:
The above doesn't compile:
fangorn:~/tmp 381> gcc -ansi -pedantic test.c
test.c:1: error: parse error before '&' token
test.c: In function `f1':
test.c:2: error: `s' undeclared (first use in this function)
test.c:2: error: (Each undeclared identifier is reported only once
test.c:2: error: for each function it appears in.)
Furthermore, calling printf without a correct declaration in scope
invokes undefined behaviour.
Dan
--
Dan Pop
DESY Zeuthen, RZ group
Email: Da*****@ifh.de This thread has been closed and replies have been disabled. Please start a new discussion. Similar topics |
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==========================================
Windows 2000 Professional
CYGWIN_NT-5.0 1.5.4(0.94/3/2)
GNU g++ version 3.2 20020927 (prerelease)
GNU objdump 2.14.90 20030901
==========================================
We can see that the same assembly code is generated for
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I have the following:
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