# stdbool

***

**1. Simple True/False Check**

```cpp
bool is_valid = true;
if (is_valid) {
  // Do something
}
```

**2. Function Parameter Validation**

```cpp
bool is_positive(int number) {
  return number > 0;
}
```

**3. Conditional Compilation**

```cpp
#ifdef DEBUG
  // Debug code
#else
  // Release code
#endif
```

**4. Loop Control**

```cpp
while (is_running) {
  // Do something
}
```

**5. Error Handling**

```cpp
if (error_code == 0) {
  // No error
} else {
  // Error occurred
}
```

**6. Boolean Algebra**

```cpp
bool a = true, b = false;
bool result = a && b; // False
```

**7. Tristate Logic**

```cpp
enum Tristate { True, False, Unknown };
Tristate state = Unknown;
```

**8. Bit Manipulation**

```cpp
bool bit_set = (flags & 0x01) != 0;
```

**9. Data Structure Flags**

```cpp
struct Node {
  bool is_leaf;
};
```

**10. Class Member Variables**

```cpp
class MyClass {
  private:
    bool is_initialized;
};
```

**11. Input Validation**

```cpp
int input;
while (!(std::cin >> input)) {
  std::cout << "Invalid input. Please enter an integer: ";
}
```

**12. Function Return Values**

```cpp
bool is_prime(int number) {
  // Check for primality
  return true;
}
```

**13. Event Handling**

```cpp
class MyEventHandler {
  public:
    void on_click() {
      is_clicked = true;
    }
    bool is_clicked = false;
};
```

**14. State Machine**

```cpp
enum State {
  Start,
  Idle,
  Running,
  Finished
};
State current_state = Start;
```

**15. Data Stream Validation**

```cpp
std::ifstream file;
file.open("data.txt");
if (!file.is_open()) {
  // Error: File could not be opened
}
```

**16. Property Accessors**

```cpp
class MyClass {
  public:
    bool get_is_valid() const {
      return is_valid;
    }
    void set_is_valid(bool new_value) {
      is_valid = new_value;
    }
  private:
    bool is_valid;
};
```

**17. Function Overloading**

```cpp
void print(int number) {
  std::cout << number;
}

void print(bool value) {
  std::cout << (value ? "true" : "false");
}
```

**18. Template Argument Deduction**

```cpp
template <typename T>
void my_function(T value) {
  bool is_true = static_cast<bool>(value);
}
```

**19. Type Conversion**

```cpp
int number = true; // Converts true to 1
```

**20. Bitwise Operations**

```cpp
bool a = true, b = false;
bool result = a | b; // True
```

**21. Logical Negation**

```cpp
bool is_not_valid = !is_valid;
```

**22. Conditional Operator**

```cpp
bool a = true;
int result = (a ? 1 : 0); // result is 1
```

**23. Function Invocation with Boolean Parameters**

```cpp
void my_function(bool is_enabled) {
  // Do something based on is_enabled
}
```

**24. Data Structure Comparisons**

```cpp
std::vector<int> a, b;
bool is_equal = (a == b);
```

**25. Range Check**

```cpp
int index = 5;
int array_size = 10;
bool is_within_range = (index >= 0 && index < array_size);
```

**26. String Comparison**

```cpp
std::string a = "hello", b = "world";
bool is_same_string = (a == b);
```

**27. File Existence Check**

```cpp
std::ifstream file("myfile.txt");
bool file_exists = file.is_open();
```

**28. Array Subscript Validation**

```cpp
int array[5];
bool is_valid_index = (index >= 0 && index < 5);
```

**29. Pointer Dereferencing Check**

```cpp
int* pointer = nullptr;
bool is_valid_pointer = (pointer != nullptr);
```

**30. Function Return Type**

```cpp
bool my_function() {
  // Do something
  return true;
}
```

**31. Loop Termination Condition**

```cpp
for (auto it = collection.begin(); it != collection.end(); ++it) {
  if (*it == target) {
    break;
  }
}
```

**32. Collection Size Check**

```cpp
std::vector<int> vec;
bool is_empty = vec.empty();
```

**33. User Input Confirmation**

```cpp
std::cout << "Are you sure you want to quit? (Y/N): ";
bool is_quitting = (std::cin.get() == 'Y');
```

**34. Runtime Feature Control**

```cpp
#ifdef FEATURE_ENABLED
  // Feature is enabled
#else
  // Feature is disabled
#endif
```

**35. Error Code Handling**

```cpp
enum ErrorCode {
  NoError,
  InvalidInput,
  OutOfMemory
};
bool handle_error(ErrorCode error_code) {
  // Handle the error
  return true;
}
```

**36. Thread Synchronization**

```cpp
std::mutex lock;
bool is_locked = false;
```

**37. Singleton Class Implementation**

```cpp
class Singleton {
  private:
    static bool is_initialized = false;
    static Singleton* instance = nullptr;
  public:
    static Singleton* get_instance() {
      if (!is_initialized) {
        instance = new Singleton();
        is_initialized = true;
      }
      return instance;
    }
};
```

**38. Memory Pool Allocation**

```cpp
class MemoryPool {
  private:
    std::vector<bool> allocated;
  public:
    void* allocate() {
      for (size_t i = 0; i < allocated.size(); ++i) {
        if (!allocated[i]) {
          allocated[i] = true;
          return &pool[i];
        }
      }
      return nullptr;
    }
    void deallocate(void* ptr) {
      for (size_t i = 0; i < allocated.size(); ++i) {
        if (&pool[i] == ptr) {
          allocated[i] = false;
          return;
        }
      }
    }
  private:
    std::vector<char> pool;
};
```

**39. State-Dependent Behavior**

```cpp
class MyClass {
  public:
    void set_state(bool new_state) {
      is_active = new_state;
    }
    void do_something() {
      if (is_active) {
        // Do something when active
      } else {
        // Do something when inactive
      }
    }
  private:
    bool is_active;
};
```

**40. Thread-Safe Data Retrieval**

```cpp
std::atomic<bool> is_ready = false;
std::atomic<bool> is_fetched = false;
std::thread fetch_thread([&]() {
  // Fetch data
  is_ready.store(true);
});
void get_data() {
  while (!is_ready.load());
  // Access data
  is_fetched.store(true);
}
```

**41. Data Structure Invalidation Check**

```cpp
class MyData {
  public:
    void invalidate() {
      is_invalid = true;
    }
    bool is_invalid = false;
};
```

**42. Signal Handling**

```cpp
volatile sig_atomic_t is_running = true;
void signal_handler(int signal) {
  is_running = false;
}
```

**43. Lazy Initialization**

```cpp
std::once_flag flag;
std::shared_ptr<MyClass> my_class;
void init_my_class() {
  my_class = std::make_shared<MyClass>();
}
std::shared_ptr<MyClass> get_my_class() {
  std::call_once(flag, init_my_class);
  return my_class;
}
```

**44. Exception Handling**

```cpp
try {
  // Do something
} catch (const std::exception& e) {
  is_error = true;
}
```

**45. Resource Management**

```cpp
class MyClass : public std::enable_shared_from_this<MyClass> {
  public:
    bool is_allocated = false;
    void allocate() {
      is_allocated = true;
    }
    void deallocate() {
      is_allocated = false;
    }
};
```

**46. Thread-Safe Function Invocation**

```cpp
std::mutex lock;
bool is_function_done = false;
void my_function() {
  // Do something
  std::lock_guard<std::mutex> guard(lock);
  is_function_done = true;
}
```

**47. Loop Optimization**

```cpp
bool is_valid = true;
for (auto it = collection.begin(); it != collection.end() && is_valid; ++it) {
  // Do something
}
```

**48. Algorithm Short-Circuiting**

```cpp
std::vector<int> vec;
bool all_positive = true;
for (auto it = vec.begin(); it != vec.end() && all_positive; ++it) {
  if (*it < 0) {
    all_positive = false;
  }
}
```

**49. Protocol Version Compatibility**

```cpp
#define PROTOCOL_VERSION 1
bool is_compatible(int version) {
  return version == PROTOCOL_VERSION;
}
```

**50. Input Validation with Regular Expressions**

```cpp
std::regex email_regex("^[a-zA-Z0-9.!#$%&'*+/=?^_`{|}~-]+@[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?(?:\\.[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?)*$");
bool is_valid_email(std::string email) {
  return std::regex_match(email, email_regex);
}
```