Determine if int is not 0 with no if statements

Question

The title is a little misleading, but I don't know what else to call it. I have an array consisting of 2 values: int array [2];

One of the values will contain 0 and the other value won't contain 0. Without the use of an if statement and most preferably, no boolean expressions, I want to determine if array[0]; contains a 0 or not. If it doesn't contain 0, it should return 1, otherwise it should return 0.

I have tried dividing the first value by itself but a Division By Zero error can occur, and I have no other alternatives to my problem.

The format I am aiming for is like this:

array[check if zero index is 0];

EDIT: Examples of this are:

array[0] = 20; 
array[1] = 0;
array[check if zero index is 0]; // index is 1

array[0] = 0; 
array[1] = 73;
array[check if zero index is 0]; // index is 0;

Why are you interested in this? just for the fun of it, or for a specific purpose? — Jens Schauder, Dec 07 '14 at 10:18
Have a look at http://stackoverflow.com/questions/1310344/why-use-when-converting-int-to-bool — , Dec 07 '14 at 10:27
@sp2danny Is there a way I can use bit-manipulation or maths instead of boolean expressions? — Hayden, Dec 07 '14 at 10:33
I want to know if this problem can be solved without an if statement or without boolean expressions. — Hayden, Dec 07 '14 at 10:36
get used to using the construct that most clearly express intent, the compiler is **way** batter that mortals at micro-optimizations anyway. — sp2danny, Dec 07 '14 at 10:37
@sp2danny, I understand that, but is there a way, with the conditions outlined, to solve this problem? — Hayden, Dec 07 '14 at 10:38
probably because the question, and eventual answers, wont be useful to someone else — sp2danny, Dec 07 '14 at 10:46

score 1 · Accepted Answer · answered Dec 07 '14 at 10:44

1

this assumes 32bit int's

((static_cast<unsigned>(-(array[0]*array[0]))&(1ul<<31))>>31)

answered Dec 07 '14 at 10:44

sp2danny

7,488
3
31
53

Determine if int is not 0 with no if statements

1 Answers1