Start with chapter 2's numbered list. A title alone can't tell us whether a task is complete. We'll give each task a title and a boolean status, then move its display logic into a function.
## Describe a task
Add this definition at the top of `tasks.tea`:
```tea
struct Task {
title: String
done: Bool
}
```
A `struct` groups named fields into a type. Fields have explicit types: `title` is a `String`, and `done` is a `Bool` (`true` or `false`). Struct definitions use braces; function and loop bodies use `end`.
Replace your string list with the `Task(...)` values in the complete checkpoint below. Named arguments make it clear which field each value supplies. The list's inferred type is now `List[Task]`.
## Give formatting a name
Add this function after the struct:
```tea
def format_task(task: Task, number: Int) -> String
const marker = if(task.done) "[x]" else "[ ]"
`${number}. ${marker} ${task.title}`
end
```
`def` introduces a function. Parameters have explicit types, and `-> String` declares the return type. Tea uses the final expression as the return value; you can also write `return` explicitly.
The `if(...) ... else ...` expression chooses one of two strings. Access a field with a dot, such as `task.done` or `task.title`. Both branches produce a `String`, so Tea can infer the type of `marker`.
Replace the loop's output statement with `@println(format_task(task, number))`, and rename its loop binding from `title` to `task`.
## Run the program
```bash
tea tasks.tea
```
```text
1. [ ] Learn Tea
2. [ ] Build a CLI
3. [x] Take a break
```
## Complete checkpoint
**`tasks.tea`**
```tea checkpoint="examples/tutorial/tasks/03-task-model/tasks.tea"
struct Task {
title: String
done: Bool
}
def format_task(task: Task, number: Int) -> String
const marker = if(task.done) "[x]" else "[ ]"
`${number}. ${marker} ${task.title}`
end
const tasks = [
Task(title: "Learn Tea", done: false),
Task(title: "Build a CLI", done: false),
Task(title: "Take a break", done: true)
]
var number = 1
for task in tasks
@println(format_task(task, number))
number = number + 1
end
```
## Try it yourself
Count completed tasks and print the count after the loop. Use a mutable counter and an `if` statement inside the loop.
Hint
Initialize `var completed = 0` before the loop. Inside it, add:
```tea
if task.done
completed = completed + 1
end
```
After the loop, print `completed`. Unlike the expression that chooses `marker`, this `if` performs an action and ends with `end`.
The task data and its presentation now have names. Next, we'll let the person running the program decide which tasks to see.
Read more: [structs](/docs/structs), [functions and return values](/docs/functions).