Printf Problem

[Ico]

Hi.I could not understand the following printf statement.Thanks for any
help.

int a=3,b=5;
printf(&a["Ya!Hello!how is this?%s],&b["junk/super]);

Neither does my compiler. If you post any code, please make sure it
compiles. I will assume you missed some quotes and ment :

printf(&a["Ya!Hello!how is this?%s"],&b["junk/super"]);

This is an old trick, not to be used in real-life code. Due to the way
arrays an pointers work in the C language, the following two lines
have the same effect:

"hello"[2]
2["hello"]

Both expressions return 'l'. If I recall correctly, the clc faq has a
detailed explanation why this is the case.

I think a equals to*[a+i].But I could not understand the use of &

In your example, the expression

&a["Ya!Hello!how is this?%s"]

is the same as

&"Ya!Hello!how is this?%s"[a]

A was set to 3 before, so this expression returns the address of the
string+3, which happens to be "Hello!how is this?%s"

The same happens with the second expression, which is used as an
argument for the %s directive in the printf format string.

 

[dis_is_eagle]

Hi.I could not understand the following printf statement.Thanks for any
help.

int a=3,b=5;
printf(&a["Ya!Hello!how is this?%s],&b["junk/super]);

I think a equals to*[a+i].But I could not understand the use of &
here.Bye.
Regards,
Eric

 

[steve]

please make sure that the code is compiled properly
syntax for printf
printf (" variables" , " control sting " );
if you want to print an address of a variable use %i or % u

thanx
http://eecsatri.blogspot.com

 

[Keith Thompson]

Hi.I could not understand the following printf statement.Thanks for any
help.

int a=3,b=5;
printf(&a["Ya!Hello!how is this?%s],&b["junk/super]);

I think a equals to*[a+i].But I could not understand the use of &
here.

No, a means *(a+i), which is equivalent to *(i+a), which is
equivalent to i[a].

You should never use this trick in real code.

 

[Christopher Benson-Manica]

please make sure that the code is compiled properly

Good advice.

syntax for printf
printf (" variables" , " control sting " );

It's difficult to tell what you meant by this, and difficult to
believe that you in fact know that the prototype of printf is

int printf( const char * format, ... );

if you want to print an address of a variable use %i or % u

Wrong. The format specifier for printing an address (which must be
cast to void * if it is not already of that type) is %p.