How macros work in C works ?

Question

I have tried to make a macro for simple square calculations but it won't work when i pass an expression to it...
Any idea why it is happening? And output?

https://code.sololearn.com/cRZOeBTWA09N/?ref=app

Answer 1

#define square(x) x*x
Macro arguments are evaluated after macro expansion.

macro definition replaces corresponding values before compilation .
if you write say
#define square(n) n*n
it'll replace all square(n) with n*n .. remember before compilation.

printf("\nsquare(4-2)) = %d",square(4-2));

this is on of the statements where you are getting wrong output logically.
let's elaborate.

square(4-2) will be replaced with 4-2*4-2
not 2*2.
this is because replacement happenes before compilation without caring 4-2 will be 2.

due to operator precedence 4-2*4-2 will be 4-(2*4)-2=4-8-2=-6.

same logic for others 😊

it's recommended to avoid using macros with parameters but here is a quick fix for your program.
just replace your macro definition with this:
#define square(x) (x)*(x)

hope you understand.

*refer also :
https://www.geeksforgeeks.org/interesting-facts-preprocessors-c/

Answer 2

Cool Thanks dude 👍

Answer 3

Aaditya Deshpande 😊👍