Efficiently make an int that has a 1 all 1s but one that is 0 stay 0
bitwise-operators, c
Solution
Assuming 2's complement:
int mask = !x + ~0;
The `!` maps any nonzero value to `0` and `0` to `1`, then we add `~0` (`-1`) to get `-1` and `0` respectively.
Problem
I have an assignment that asks to do a number of functions only using these operators: ! ~ & ^ | + << >> In some of the problems it is useful to make some integer, x, become all 1s if it contains any 1s but stay 0 if it is 0. The reason I do this is so I can return y or z like this: ``` // One of the two conditional values is now 0 int conditionalA = mask&y; int conditionalB = ~mask&z; // One of the values is combined with 0 using | int out = conditionalA|conditionalB; return out; ``` where I made mask like this: ``` // Make any x other than 0 all 1s int mask = x; mask |= mask>>1; mask |= mask>>2; mask |= mask>>4; mask |= mask>>8; mask |= mask>>16; mask |= mask<<1; mask |= mask<<2; mask |= mask<<4; mask |= mask<<8; mask |= mask<<16; ``` There must be a better way to make mask all 1s or 0s but I can't think of a more efficient solution. Again, it is important that 0 remains 0 if x was 0. Edit: If statements are not an option