🔢 C++ Operator Precedence – Understand Expression Evaluation Order
🧲 Introduction – What Is Operator Precedence in C++?
Operator precedence in C++ determines the order in which operators are evaluated in an expression. When multiple operators are used together, precedence helps avoid ambiguity by specifying which operations are performed first, ensuring expressions yield correct results.
🎯 In this guide, you’ll learn:
- What operator precedence is and why it matters
- Complete precedence and associativity table
- Examples that illustrate precedence rules
- How to use parentheses to override default behavior
✅ What Is Operator Precedence?
It’s the priority ranking of operators—operators with higher precedence are evaluated before those with lower precedence in the same expression.
int result = 10 + 5 * 2; // result = 10 + (5 * 2) = 20
Here, * has higher precedence than +.
🔄 What Is Associativity?
When operators have the same precedence, associativity determines the direction of evaluation—either left-to-right or right-to-left.
int x = y = z = 5; // Right-to-left associativity for `=`
🧮 C++ Operator Precedence Table
| Precedence | Operators | Associativity |
|---|---|---|
| Highest | :: | Left to right |
(), [], ->, . | Left to right | |
++, --, +(unary), -, !, ~ | Right to left | |
*, /, % | Left to right | |
+, - | Left to right | |
<<, >> | Left to right | |
<, <=, >, >= | Left to right | |
==, != | Left to right | |
& | Left to right | |
^ | Left to right | |
| ` | ` | |
&& | Left to right | |
| ` | ||
?: | Right to left | |
=, +=, -=, etc. | Right to left | |
, | Left to right | |
| Lowest |
✏️ Example – Complex Expression
int a = 5, b = 10, c = 20;
int result = a + b * c; // result = 5 + (10 * 20) = 205
➕ With Parentheses
int result = (a + b) * c; // result = (5 + 10) * 20 = 300
⚠️ Common Pitfalls
| ❌ Mistake | ✅ Fix |
|---|---|
| Relying on operator order blindly | Use parentheses for clarity |
| Misunderstanding right/left associativity | Learn which operators evaluate right-to-left |
| Unexpected results in assignments | Use () to prioritize evaluation |
🧠 Best Practices
- Use parentheses to clarify evaluation order
- Don’t assume others understand precedence as well as you do
- Avoid writing overly complex expressions in one line
📌 Summary – Recap & Next Steps
🔍 Key Takeaways:
- Operator precedence determines the order of operations
- Associativity resolves tie-breaking between same-level operators
- Use parentheses to enforce or override precedence
- Understanding precedence helps avoid logic errors in expressions
⚙️ Real-World Relevance:
Operator precedence is critical in math expressions, loop conditions, control logic, and bitwise computation, where correct evaluation order ensures correct results.
❓ FAQs – C++ Operator Precedence
❓ What operator has the highest precedence?
✅ Scope resolution :: and postfix operators like (), [], and .
❓ What is left-to-right associativity?
✅ Evaluation starts from the leftmost operator and proceeds right.
❓ Do logical operators have low precedence?
✅ Yes. && and || are evaluated after comparison and arithmetic operators.
❓ How do I control operator precedence?
✅ Use parentheses to group expressions explicitly.
❓ Can associativity override precedence?
❌ No. Precedence is checked first. Associativity resolves order only among operators of the same precedence level.
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