Toán tử, biểu thức và chuyển đổi

#include <iostream>

int main() {
    // Precedence trap #1: bitwise vs comparison
    int x = 5;
    // This does NOT check if bit 1 is set:
    if (x & 1 == 0) {              // Parsed as: x & (1 == 0) → x & 0 → 0
        std::cout << "Never reached!\n";
    }
    // Correct:
    if ((x & 1) == 0) {            // Parentheses fix the grouping
        std::cout << "Even\n";
    }

    // Precedence trap #2: ternary vs assignment
    int a = 1, b = 2;
    int result = a > b ? a : b = 10;  // Parsed as: (a > b ? a : b) = 10 — ERROR!
    // Correct:
    int correct = (a > b) ? a : b;    // Parenthesize for clarity

    // Precedence trap #3: pointer dereference vs member access
    // (*ptr).member  vs  ptr->member  — both are equivalent
    // *ptr.member    is parsed as *(ptr.member) — usually a compile error

    // Short-circuit evaluation
    int* ptr = nullptr;
    // Safe: the second operand is NOT evaluated if the first is false
    if (ptr != nullptr && *ptr > 0) {
        std::cout << "Value: " << *ptr << '\n';
    }
    // The && and || operators guarantee left-to-right evaluation and short-circuit
    // Overloaded && and || do NOT short-circuit — avoid overloading them
}

#include <iostream>
#include <cstdint>

class Base {
public:
    virtual ~Base() = default;
    virtual void speak() { std::cout << "Base\n"; }
};

class Derived : public Base {
public:
    void speak() override { std::cout << "Derived\n"; }
    void only_in_derived() { std::cout << "Special!\n"; }
};

int main() {
    // static_cast — compile-time checked, for "natural" conversions
    double pi = 3.14159;
    int truncated = static_cast<int>(pi);    // Explicit: you acknowledge the truncation
    std::cout << truncated << '\n';          // 3

    // dynamic_cast — runtime-checked, for safe downcasting in class hierarchies
    Base* base_ptr = new Derived();
    Derived* derived_ptr = dynamic_cast<Derived*>(base_ptr);
    if (derived_ptr) {                       // Check for success!
        derived_ptr->only_in_derived();       // Safe
    }

    // const_cast — adds or removes const (use sparingly!)
    const int ci = 42;
    // int& mutable_ref = const_cast<int&>(ci);  // Legal but modifying ci is UB!
    // Only valid use: calling a non-const API with a const object you know won't be modified

    // reinterpret_cast — reinterprets the bit pattern (dangerous!)
    std::int64_t address = reinterpret_cast<std::int64_t>(base_ptr);
    std::cout << "Address: " << address << '\n';

    // C-style cast: (int)pi — NEVER use this in C++
    // It tries static_cast, then const_cast, then reinterpret_cast — 
    // you don't know which one was applied!

    delete base_ptr;
}