How to check whether a number is positive/zero/negative without using conditional statements in Rust

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fn main() {
    let n: i32 = 89;

    // create text labels for each possible case
    let result = [
        "negative",  // index 0
        "zero",      // index 1
        "positive",  // index 2
    ];

    // compute an index without using any conditional statements
    // (n > 0) becomes 1 if true, 0 if false
    // (n < 0) becomes 1 if true, 0 if false
    // index = 1 + (n > 0) - (n < 0)
    let index: usize = (1 + (n > 0) as i32 - (n < 0) as i32) as usize;

    // print the classification
    println!("{}", result[index]);

    /*
       Checks:

       n = -3
       (n > 0) = 0
       (n < 0) = 1
       index = 1 + 0 - 1 = 0
       result = negative

       n = 0
       (n > 0) = 0
       (n < 0) = 0
       index = 1 + 0 - 0 = 1
       result = zero

       n = 89
       (n > 0) = 1
       (n < 0) = 0
       index = 1 + 1 - 0 = 2
       result = positive
    */
}



/*
run:

positive

*/

 



answered Jun 27 by avibootz

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