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Listing tasks

Learn to print tasks formatted with listTasks.

Listing tasks

Now we will write the listTasks function. It prints the list in a readable form. It takes a const std::vector<Task>& parameter; const because the list is only read, not modified.

In the body, a for loop walks each task by index, numbers it with i + 1, and prints tasks[i].title. This gives the reader 'which task' information and makes the list readable.

Walking with a loop

To walk a vector by index, you use a classic for loop: for (size_t i = 0; i < tasks.size(); ++i). size_t is an unsigned integer type that matches the return type of size().

Inside the loop, tasks[i] accesses the i-th element; tasks[i].title gets its title. Writing i + 1 shows the user a number starting from 1, because humans count from 1, not 0. This makes the list output readable.

Practice The listTasks function

Define void listTasks(const std::vector<Task>& tasks). In the body, walk each task with for (size_t i = 0; i < tasks.size(); ++i); on each line print i + 1, ". ", and tasks[i].title. In main, add "Ekmek al" and "Süt al" with addTask, then call listTasks(tasks).

Starter code

main.cpp
#include <iostream>
#include <string>
#include <vector>

struct Task {
    std::string title;
    bool done;
};

void addTask(std::vector<Task>& tasks, const std::string& title) {
    Task t;
    t.title = title;
    t.done = false;
    tasks.push_back(t);
}

// Define the listTasks function

int main() {
    std::vector<Task> tasks;
    addTask(tasks, "Ekmek al");
    addTask(tasks, "Süt al");
    // Add a listTasks call
    return 0;
}

Sample solution

main.cpp
#include <iostream>
#include <string>
#include <vector>

struct Task {
    std::string title;
    bool done;
};

void addTask(std::vector<Task>& tasks, const std::string& title) {
    Task t;
    t.title = title;
    t.done = false;
    tasks.push_back(t);
}

void listTasks(const std::vector<Task>& tasks) {
    for (size_t i = 0; i < tasks.size(); ++i) {
        std::cout << i + 1 << ". " << tasks[i].title << "\n";
    }
}

int main() {
    std::vector<Task> tasks;
    addTask(tasks, "Ekmek al");
    addTask(tasks, "Süt al");
    listTasks(tasks);
    return 0;
}

Expected output

1. Ekmek al
2. Süt al

Questions and answers

Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.

1 What is the first line of listTasks output?

main.cpp
std::vector<Task> tasks;
addTask(tasks, "Ekmek al");
addTask(tasks, "Süt al");
listTasks(tasks);
  • 2. Süt al
  • 1. Ekmek al Correct answer
  • Ekmek al
  • 1

Explanation: The first task has number 1 and title 'Ekmek al'; the first line is '1. Ekmek al'.

2 Match each expression to its meaning

Term Meaning
void listTasks Function signature
for (size_t i... Loop
tasks[i].title Element access
listTasks(tasks) Call

3 listTasks body

Question 
for (size_t i = 0; i < ____.size(); ++i) { std::cout << i + 1; }
Answer 
for (size_t i = 0; i < tasks.size(); ++i) { std::cout << i + 1; }

Explanation: for (size_t i = 0; i < tasks.size(); ++i) walks the tasks.

All lessons in Beginner

1 C++ basics

  1. What is C++?
  2. Your first program
  3. std::cout
  4. std::cin
  5. Comments
  6. Summary - C++ basics

2 Variables

  1. Declaring variables
  2. auto
  3. const
  4. constexpr
  5. Type conversion
  6. Summary - Variables

3 Data types

  1. Integer types
  2. Floating-point types
  3. bool and char
  4. std::string
  5. sizeof
  6. Summary - Data types

4 Project: Calculator

  1. Project design
  2. Add and subtract
  3. Multiply and divide
  4. Error handling
  5. Putting it together

5 Operators

  1. Arithmetic operators
  2. Assignment operators
  3. Comparison operators
  4. Logical operators
  5. Bitwise operators
  6. Summary - Operators

6 Strings

  1. std::string basics
  2. String concatenation
  3. String length
  4. Substring
  5. String search
  6. Summary - Strings

7 Conditionals

  1. The if statement
  2. else and else if
  3. The switch statement
  4. The ternary operator
  5. Nested conditionals
  6. Summary - Conditionals

8 Loops

  1. The for loop
  2. The while loop
  3. The do-while loop
  4. Range-based for
  5. break and continue
  6. Summary - Loops

9 Project: Shopping cart

  1. Cart design
  2. Adding products
  3. Calculating totals
  4. Listing the cart
  5. Putting it together

10 Arrays

  1. C-style arrays
  2. Array access
  3. std::array
  4. Multidimensional arrays
  5. Arrays and loops
  6. Summary - Arrays

11 std::vector

  1. Declaring vectors
  2. push_back
  3. size and at
  4. Vector access
  5. Vector loop
  6. Summary - std::vector

12 Functions

  1. Defining functions
  2. Return values
  3. Parameters
  4. Function overloading
  5. Default parameters
  6. Summary - Functions

13 References

  1. What is a reference?
  2. Declaring references
  3. Reference parameters
  4. const references
  5. Dangling references
  6. Summary - References

14 Pointer basics

  1. What is a pointer?
  2. The & address operator
  3. Pointer dereference
  4. nullptr
  5. Pointer arithmetic
  6. Summary - Pointer basics

15 Project: To-do CLI

  1. Task model
  2. Adding tasks
  3. Listing tasks
  4. Completing tasks
  5. Putting it together

16 Advanced string operations

  1. String streams
  2. stoi and stod
  3. to_string
  4. String comparison
  5. String modification
  6. Summary - Advanced strings

17 Structs

  1. Defining structs
  2. Using structs
  3. Struct and function
  4. Array of structs
  5. Nested structs
  6. Summary - Structs

18 Exception basics

  1. try/catch
  2. throw
  3. std::exception
  4. Custom exceptions
  5. catch all
  6. Summary - Exceptions

19 Namespaces

  1. Defining namespaces
  2. using
  3. std namespace
  4. Nested namespaces
  5. Namespace alias
  6. Summary - Namespaces

20 Beginner final

  1. Project design
  2. Data model
  3. Business logic
  4. Error handling
  5. Putting it together