Sorting your own struct in Mojo

Conform to Comparable and the standard sort will order your values.

from std.builtin.sort import sort


@fieldwise_init
struct Card(ImplicitlyCopyable, Movable, Comparable):
    var rank: Int

    def __lt__(self, other: Self) -> Bool:
        return self.rank < other.rank

    def __eq__(self, other: Self) -> Bool:
        return self.rank == other.rank


def main():
    var hand = [Card(7), Card(2), Card(10), Card(5)]
    sort(hand)
    for card in hand:
        print(card.rank)

How it works

1. Comparable is satisfied by __lt__ and __eq__ together.
2. Both compare the rank field, which is what ordering a card means here.
3. sort(hand) rearranges the list in place, low rank first.

Keywords and builtins used here

• Int
• Movable
• def
• for
• main
• print
• return
• self
• struct
• var

The run, in numbers

Lines

19

Characters to type

369

Tokens

102

Three-star pace

70 tpm

At the three-star pace of 70 tokens a minute, this run takes about 87 seconds.

Type this snippet

Step 5 of 5 in Traits, step 20 of 22 in Structs & traits.

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