rustLogic errorMedium

Inconsistent ordering and equality in custom types

Time: 0:00

BugFind the bug and fix the code

What it should do

Determine if a custom type instance is ordered correctly. Example: is_ordered(x) -> bool

What happens instead

The compiler error: 'the trait `PartialOrd` is not implemented for `MyType`'

use std::cmp::Ordering;

struct MyType(i32);

impl PartialEq for MyType {
    fn eq(&self, other: &Self) -> bool {
        self.0 == other.0
    }
}

impl PartialOrd for MyType {
    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
        Some(self.0.partial_cmp(&other.0)?)
    }
}

fn is_ordered(a: MyType, b: MyType) -> bool {
    a < b
}

fn main() {
    let a = MyType(5);
    let b = MyType(10);
    println!("Is ordered: {}", is_ordered(a, b));
}

Test a custom input to verify an edge case (e.g. empty lists, negative numbers, duplicates).

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Hints

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Hint 3

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This bug belongs to the logic errors pattern

The wrong operator, an inverted condition, a formula the right way round but backwards.

Learn the logic errors pattern Step through your own code

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use std::cmp::Ordering; struct MyType(i32); impl PartialEq for MyType { fn eq(&self, other: &Self) -> bool { self.0 == other.0 } } impl PartialOrd for MyType { fn partial_cmp(&self, other: &Self) -> Option<Ordering> { Some(self.0.partial_cmp(&other.0)?) } } fn is_ordered(a: MyType, b: MyType) -> bool { a < b } fn main() { let a = MyType(5); let b = MyType(10); println!("Is ordered: {}", is_ordered(a, b)); }

Inconsistent ordering and equality in custom types

What it should do

What happens instead

More logic errors to practise

Inconsistent ordering and equality in custom types

What it should do

What happens instead

More logic errors to practise