Data types in #define function-like macros

Question

I'm trying to make a macros that calculates 2 ⁿ and 2 ^{n - 1}. That would be:

#define b(n) (2 << (n))
#define a(n) ((b(n))-1)

However for some reason this cast it as int, but I'm willing to use unsigned long int. Does anyone know how to solve this? I have thought about using inline functions, however I don't fully grasp the difference between function-like macros and inline functions.

Answer 1

OP wants unsigned long int, then use that type in your macro

#define b(n) (1UL<<((unsigned)(n)))

When OP used (2 << (n)), the result is type int, as 2 is an int. Operator << with an int and unsigned results in int. Instead use unsigned throughout.

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Further, to emulate power(2,n), certainly the OP wanted to use 1 shifted left, rather than 2 shifted left.