README.md

Basics

Example	Topic
ControlFlow	if/else, if with initializer, switch and [[fallthrough]], loops, break/continue/goto
Initialization	default, value, direct, copy, list and aggregate initialization
Operations	arithmetic, logical (short-circuit) and bitwise operators
TypeQualifier	const, constexpr, consteval, constinit, mutable, volatile
Attributes	[[nodiscard]], [[maybe_unused]], [[fallthrough]], [[deprecated]], [[likely]], [[assume]] (draft)

1. Initialization

int a;             // default initialization: indeterminate value, reading it is UB
int b{};           // value initialization: 0
int c(42);         // direct initialization
int d = 42;        // copy initialization
int e{42};         // list initialization: rejects narrowing (int e{4.2} does not compile)
Point p{.x = 1};   // designated initializer (C++20, aggregates only)

• Prefer braces {}: they always initialize and reject narrowing.
• T obj(); does not create an object. It declares a function (the "most vexing parse").
• std::vector<int>{3, 7} holds the two elements 3 and 7, while std::vector<int>(3, 7) holds three 7s.

2. Operators

• Integer division truncates toward zero. % keeps the sign of the left operand.
• Unsigned arithmetic wraps around. Signed overflow is undefined behavior.
• && and || short-circuit: the right side runs only if needed.
• Prefix ++x returns the new value; postfix x++ returns a copy of the old one.

3. const vs constexpr vs consteval vs constinit

Keyword	Guarantees
const	the value cannot change after initialization (may be known only at run time)
constexpr	the value is computed at compile time; constexpr functions may run there
consteval	the function must run at compile time (C++20)
constinit	a static variable is initialized at compile time but stays mutable (C++20)

Use constexpr instead of #define for constants: it has a type, a scope, and shows up in the debugger.