#define f(g,g2) g##g2

Question

#define f(g,g2) g##g2
main()
{
int var12=100;
printf("%d",f(var,12));
}

The above program prints 100 in c by concatenating var and 12. How does g##g2 work??

Answer 1

## just pastes tokens together. It is a preprocessor directive.

E.g.

#define PASTE(a,b)  a##b

int i=PASTE(1,2);  /* int i=12; */