Counter-intuitive operator precedence

While debugging, I spotted a very counter-intuitive operator precedence evaluation.

Question: is it just me, or does the following code seem highly susceptible to bugs. If the code is indeed correct, does it serve as a nice example why we should be cautious about omitting parentheses? A warning would have saved me several hours of debugging...

fn test() -> Bool:
    return True

fn main():
    let A: SIMD[DType.int32, 1] = 10
    let B: SIMD[DType.int32, 1] = 10

    if A != B & test(): # assumed operator precedence
        print("A: not expected but observed")
    else: 
        print("A: expected but not observed")


    if (A != B) & test(): # explicit
        print("B: not expected and not observed")
    else: 
        print("B: expected and observed")

fn test() -> Bool:
    return True

fn main():
    let A: SIMD[DType.int32, 1] = 10
    let B: SIMD[DType.int32, 1] = 10

    if A != B & test(): # assumed operator precedence
        print("A: not expected but observed")
    else: 
        print("A: expected but not observed")


    if (A != B) & test(): # explicit
        print("B: not expected and not observed")
    else: 
        print("B: expected and observed")

Modular•3y ago•

3 replies

Henk-Jan Lebbink

Counter-intuitive operator precedence

fn test() -> Bool:
    return True

fn main():
    let A: SIMD[DType.int32, 1] = 10
    let B: SIMD[DType.int32, 1] = 10

    if A != B & test(): # assumed operator precedence
        print("A: not expected but observed")
    else: 
        print("A: expected but not observed")


    if (A != B) & test(): # explicit
        print("B: not expected and not observed")
    else: 
        print("B: expected and observed")

fn test() -> Bool:
    return True

fn main():
    let A: SIMD[DType.int32, 1] = 10
    let B: SIMD[DType.int32, 1] = 10

    if A != B & test(): # assumed operator precedence
        print("A: not expected but observed")
    else: 
        print("A: expected but not observed")


    if (A != B) & test(): # explicit
        print("B: not expected and not observed")
    else: 
        print("B: expected and observed")

Counter-intuitive operator precedence

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