InfiniteCoder01 · September 15, 2025 16:47 · Sep 15, 2025
diff --git a/challenge.c b/challenge.c
@@ -0,0 +1,74 @@
+#include <stdbool.h>
+#include <stdlib.h>
+#include <stdio.h>
+
+#define FAT_PTR_IMPL(T) \
+typedef struct { \
+    void *ptr; \
+    T *meta; \
+} FatPtr ## T;
+
+typedef enum {
+    Rock,
+    Paper,
+    Scissors,
+} Move;
+
+typedef struct RockPaperScissorsVtable {
+    Move (*play)(void *self);
+} RockPaperScissorsVtable;
+
+FAT_PTR_IMPL(RockPaperScissorsVtable);
+
+// Returns whether player 1 won
+bool battle(FatPtrRockPaperScissorsVtable p1, FatPtrRockPaperScissorsVtable p2) {
+    const Move move1 = p1.meta->play(p1.ptr);
+    const Move move2 = p2.meta->play(p2.ptr);
+    if ((move1 == Rock && move2 == Scissors)
+        || (move1 == Scissors && move2 == Paper)
+        || (move1 == Paper && move2 == Rock)) {
+        return true;
+    } else {
+        return false;
+    }
+}
+
+typedef struct {} RandomPlayer;
+Move random_player_play(RandomPlayer *self) {
+    const int r = rand() % 3;
+    printf("> %d\n", r);
+    if (r == 0) return Rock;
+    else if (r == 1) return Paper;
+    else if (r == 2) return Scissors;
+    puts("unreachable executed!");
+    exit(-1);
+}
+
+RockPaperScissorsVtable RANDOM_PLAYER_VTABLE = {
+    .play = (void *)random_player_play,
+};
+
+int main() {
+    srand(128);
+    RandomPlayer p1inner;
+    RandomPlayer p2inner;
+    FatPtrRockPaperScissorsVtable p1 = {
+        .ptr = &p1inner,
+        .meta = &RANDOM_PLAYER_VTABLE,
+    };
+    FatPtrRockPaperScissorsVtable p2 = {
+        .ptr = &p2inner,
+        .meta = &RANDOM_PLAYER_VTABLE,
+    };
+    puts("Best of 3!");
+    int p1_won = 0;
+    for (int i = 0; i < 3; i++) {
+        if (battle(p1, p2)) p1_won++;
+    }
+    if (p1_won >= 2) puts("P1 wins!");
+    else puts("P2 wins!");
+
+    return 0;
+}
+
+
diff --git a/challenge.rs b/challenge.rs
@@ -0,0 +1,52 @@
+use rand::rng;
+
+enum Move {
+    Rock,
+    Paper,
+    Scissors,
+}
+
+trait RockPaperScissors {
+    fn play(&mut self) -> Move;
+}
+
+// Returns whether player 1 won
+fn battle(p1: &mut dyn RockPaperScissors, p2: &mut dyn RockPaperScissors) -> bool {
+    use Move::*;
+    match (p1.play(), p2.play()) {
+        (Rock, Scissors) | (Scissors, Paper) | (Paper, Rock) => true,
+        _ => false,
+    }
+}
+
+struct RandomPlayer;
+impl RockPaperScissors for RandomPlayer {
+    fn play(&mut self) -> Move {
+        use rand::Rng as _;
+        let mut rng = rng();
+        match rng.random::<u8>() % 3 {
+            0 => Move::Rock,
+            1 => Move::Paper,
+            2 => Move::Scissors,
+            _ => unreachable!(),
+        }
+    }
+}
+
+fn main() {
+    let mut p1 = RandomPlayer;
+    let mut p2 = RandomPlayer;
+    println!("Best of 3!");
+    let p1_won = (0..3).fold(0, |p1_won, _| {
+        if battle(&mut p1, &mut p2) {
+            p1_won + 1
+        } else {
+            p1_won
+        }
+    });
+    if p1_won >= 2 {
+        println!("P1 wins!");
+    } else {
+        println!("P2 wins!");
+    }
+}