Can I find the factorial of a number using conditional operator in a macro definition?
#define fact(n) ( n == 0 ? 1 ; (n*(fact(n-1) ) ) )
since recursive definition is not allowed in macros, is there any work around?
Thanks,
Anoop.
Can I find the factorial of a number using conditional operator in a macro definition?
#define fact(n) ( n == 0 ? 1 ; (n*(fact(n-1) ) ) )
since recursive definition is not allowed in macros, is there any work around?
Thanks,
Anoop.
You can solve the problem by removing the recursion and using a while-loop or such instead.
Shiro
As far as I now, the ?: operator is C++ not C. Correct me if wrong.
Second, it is not:
But:Code:#define fact(n) ( n == 0 ? 1 ; (n*(fact(n-1) ) ) )
Code:#define fact(n) ( n == 0 ? 1 :(n*(fact(n-1) ) ) )
Nothing more to tell about me...
Happy day =)
first off, ? exists in C, second off, changing that still doesn't make that macro make sense...
Essentially, macros are a shortcut for replacing certain types of things in the code when you compile it. for example, if I type this into my code:
#define MAX 30
when I compile my code, every instance of MAX will be replaced by 30...
I think if he defines n to a number before that recursive macro, it MIGHT be compilable, but his program's size may increase exponentally relative the the value of n....
Okie that ";" obviously was a typo. Sorry for that.
As tzuchan has pointed out, it exists in C.
Now, defining N might not work since the compiler would look for
#define TOKEN VALUE
and would complain if the VALUE is expressed in terms of TOKEN again. Moreover, if you define N, you dont need to put a conditional operator.
What I wanted to know was if someone has cheated the compiler and calculated the factorial using the conditional operator in a macro.
Generalizing, has anyone, used recursive MACRO?
Thanks,
Anoop.
>Generalizing, has anyone, used recursive MACRO?
You can't. It simply replaces the text. Take this code for example:
This is what it might look like after the macros are dealt with:Code:#define for if( 0 ); else for int main( void ) { int i; for( i = 0; i < 5; ++i ) putc( '0' + i ); return 0; }
All it does is replaces every instance of 'for' in the code with 'if( 0 ); else for'. No recursion. Can't do it.Code:int main( void ) { int i; if( 0 ); else for( i = 0; i < 5; ++i ) putc( '0' + i ); return 0; }
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You can use a macro for calculating the factorial of n like this:
Note that if you use such a macro, then in the function where you use it, the variables, n, f and i must have been declared before the macro can be used. A macro can't be recursive, since a macro isn't a call to something. As XSquared said, it is a replacement of some text.Code:#define FAC(n) \ for (f = 1, i = 2; i <= n; i++) \ { \ f *= i; \ }
