pub fn Graph(comptime T: type) type {
    return struct {
        constants: std.ArrayList(T),

        pub fn init(allocator: *std.mem.Allocator) Graph(T) {
            return .{ .constants = std.ArrayList(T).init(allocator) };
        }
    };
}

pub fn constant(comptime T: type, graph: *Graph(T), value: T) !void {
    try graph.constants.append(value);
}

test "create graph" {
    var arena = std.heap.ArenaAllocator.init(std.heap.page_allocator);
    defer arena.deinit();
    const allocator = &arena.allocator;

    var graph = Graph(i32).init(allocator);
    const x = try constant(i32, &graph, 5);
    const y = try constant(i32, &graph, 10);
}