1 files changed, 85 insertions, 0 deletions
diff --git a/src/stack.zig b/src/stack.zig
new file mode 100644
index 0000000..41f7415
--- /dev/null
+++ b/src/stack.zig
@@ -0,0 +1,85 @@
+const std = @import("std");
+const vector = std.meta.Vector(2, u64);
+
+pub const Stack = struct {
+    data: std.ArrayList(u64),
+    pub fn clear(self: *Stack) void {
+        self.data.clearRetainingCapacity();
+    }
+    pub fn deinit(self: *Stack) void {
+        self.data.deinit();
+    }
+    pub fn duplicate(self: *Stack) !void {
+        if (self.data.items.len > 0) {
+            try self.push(self.data.items[self.data.items.len - 1]);
+        }
+    }
+    pub fn init(comptime allocator: std.mem.Allocator) Stack {
+        return Stack{
+            .data = std.ArrayList(u64).init(allocator),
+        };
+    }
+    pub fn pop(self: *Stack) u64 {
+        return if (self.data.popOrNull()) |v| v else 0;
+    }
+    pub fn popVector(self: *Stack) [2]u64 {
+        const b = if (self.data.popOrNull()) |v| v else 0;
+        const a = if (self.data.popOrNull()) |v| v else 0;
+        return [2]u64{ a, b };
+    }
+    pub fn push(self: *Stack, n: u64) !void {
+        try self.data.append(n);
+    }
+    pub fn pushVector(self: *Stack, v: [2]u64) !void {
+        try self.data.appendSlice(v[0..2]);
+    }
+    pub fn swap(self: *Stack) !void {
+        const v = self.popVector();
+        try self.pushVector([2]u64{ v[1], v[0] });
+    }
+};
+
+test "clear" {
+    var s = Stack.init(std.testing.allocator);
+    defer s.deinit();
+    s.clear();
+    try std.testing.expect(s.pop() == 0);
+    try s.pushVector([2]u64{ 1, 2 });
+    s.clear();
+    try std.testing.expect(s.pop() == 0);
+}
+test "duplicate" {
+    var s = Stack.init(std.testing.allocator);
+    defer s.deinit();
+    try s.duplicate();
+    try std.testing.expectEqual(s.popVector(), @as(vector, [2]u64{ 0, 0 }));
+    try s.pushVector([2]u64{ 1, 2 });
+    try s.duplicate();
+    try s.duplicate();
+    try std.testing.expectEqual(s.popVector(), @as(vector, [2]u64{ 2, 2 }));
+    try std.testing.expectEqual(s.popVector(), @as(vector, [2]u64{ 1, 2 }));
+}
+test "push and pop" {
+    var s = Stack.init(std.testing.allocator);
+    defer s.deinit();
+    try std.testing.expect(s.pop() == 0);
+    try std.testing.expectEqual(s.popVector(), @as(vector, [2]u64{ 0, 0 }));
+    try s.push(1);
+    try std.testing.expect(s.pop() == 1);
+    try std.testing.expect(s.pop() == 0);
+    try s.pushVector([2]u64{ 2, 3 });
+    try std.testing.expect(s.pop() == 3);
+    try std.testing.expectEqual(s.popVector(), @as(vector, [2]u64{ 0, 2 }));
+}
+test "swap" {
+    var s = Stack.init(std.testing.allocator);
+    defer s.deinit();
+    try s.swap();
+    try std.testing.expectEqual(s.popVector(), @as(vector, [2]u64{ 0, 0 }));
+    try s.push(1);
+    try s.swap();
+    try std.testing.expectEqual(s.popVector(), @as(vector, [2]u64{ 1, 0 }));
+    try s.push(2);
+    try s.swap();
+    try std.testing.expectEqual(s.popVector(), @as(vector, [2]u64{ 2, 0 }));
+}