lvalue and rvalue

Overview

lvalue rvalue
Description Refers to a memory location Value resulting from an expression
Position Left of '=' Right of '='
Name L = Left/Locator (Memory) R = RIght
Can assign ✅ ❌
Can read ✅ ✅
Others Has name/variable/address
Examples
(int a,b,c)

Examples

int a = 1, b = 2, c = 3;

// === Normal use ===
a = b + c; // a - lvalue, b + c - 
a = 7; // a - lvalue, 7 - rvalue

// === Weird but still able to compile ===
// Breakdown:
// - (b = c) -> b assigned to c, returns a rvalue
// - c = a + (return value)
// - NOTE: This is different from: "c = a + b = c;" which is illegal
c = a + (b = c);

Illegal usage

int a = 1, b = 2, c = 3;
// === Clearly wrong ===


// === Less clearly wrong
// Operator precedence: '+' has higher precedence than '='
c = a + b = c;


// Why? (a = b) => rvalue, which can't be assigned to c
(a = b) = c; 
(((a = b) = c) = 5);