CODEWITHSUNDEEP
rust
realtebo
realtebo

Reputation: 25637

How to implement comparison between two diffrent types?

First "type" is an enum

pub enum Symbol {
    X,
    O,
}

Second is a also an enum

pub enum CellContent {
    Move(Symbol),
    None,
}

Having these 3 only variants allowed

let cellX = CellContent::Move(Symbol::X);
let cellO = CellContent::Move(Symbol::O);
let cellEmpty = CellContent::None;

How can I compare a CellContent with a Symbol ?

assert_eq(cellX, Symbol::X);
assert_eq(cellY, Symbol::X);

I tried

impl PartialEq<Symbol> for CellContent {
    fn eq(&self, other: &Symbol) -> bool {
        if self == CellContent::None {
            return false;
        }
        true;
    }
}

the first comparison doesn't compile because can't compare &structs::CellContent with structs::CellContent

and obviously i cannot return true in the other case but I must compare if self is a Move(Symbol::X) and other is a Symbol::X, or CellConent is a Move(Symbol::) and other is a Symbol::X

I have no idea of how to write these 3 comparison

Upvotes: 1

Views: 280

Answers (1)

Jeremy Meadows
Jeremy Meadows

Reputation: 2561

You should derive Eq and PartialEq for your enums first, so that they can be compared to themselves. After that, you can check if a move is equal to a symbol, or always return false if there is no move:

#[derive(Debug, PartialEq, Eq)]
pub enum Symbol {
    X,
    O,
}

#[derive(Debug, PartialEq, Eq)]
pub enum CellContent {
    Move(Symbol),
    None,
}

impl PartialEq<Symbol> for CellContent {
    fn eq(&self, other: &Symbol) -> bool {
        match self {
            CellContent::Move(symbol) => symbol == other,
            CellContent::None => false,
        }
    }
}

fn main() {
    let cellX = CellContent::Move(Symbol::X);
    let cellO = CellContent::Move(Symbol::O);
    let cellEmpty = CellContent::None;

    assert_eq!(cellX, CellContent::None);
}

(I also derived Debug to see prettier error messages)

Upvotes: 1

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