Check if a number x is positive (x>0) by ONLY using bitwise operators in C

Question

isPositive - return true if x > 0, otherwise false

Example: isPositive(-1)

Legal ops: ! ~ & ^ | + << >>

Max ops: 8

Note: No conditional statements are allowed.

inline bool isPositive(int32_t x) {
  return ???;
}

Answer 1

int isPositive(int x) {
   return !((x&(1<<31)) | !x);
}

x&(1<<31 is to check if the number is negative.

!x is to check if the number is zero.

A number is positive if it's not negative and not zero.

Answer 2

return !((x & 0x80000000) >> 31 | !x);