In order to properly evaluate an expression such as `4 + 2 * 3`

, we must understand both what the operators do, and the correct order to apply them. The order in which operators are evaluated in a compound expression is called **operator precedence**. Using normal mathematical precedence rules (which states that multiplication is resolved before addition), we know that the above expression should evaluate as `4 + (2 * 3) = 10`

.

In C++, all operators are assigned a level of precedence. Those with the highest precedence are evaluated first. You can see in the table below that multiplication and division (precedence level 5) have a higher precedence than addition and subtraction (precedence level 6). The compiler uses these levels to determine how to evaluate expressions it encounters.

If two operators with the same precedence level are adjacent to each other in an expression, the **associativity rules** tell the compiler whether to evaluate the operators from left to right or from right to left. For example, in the expression `3 * 4 / 2`

, the multiplication and division operators are both precedence level 5. Level 5 has an associativity of left to right, so the expression is resolved from left to right: `(3 * 4) / 2 = 6`

.

Prec/Ass | Operator | Description | Example |
---|---|---|---|

1 None |
:: :: |
Global scope (unary) Class scope (binary) |
::g_nGlobalVar = 5; Class::m_nMemberVar = 5; |

2 L->R |
() () () [] . -> ++ –– typeid const_cast dynamic_cast reinterpret_cast static_cast |
Parenthesis Function call Implicit assignment Array subscript Member access from object Member access from object ptr Post-increment Post-decrement Run-time type information Cast away const Run-time type-checked cast Cast one type to another Compile-time type-checked cast |
(x + y) * 2; Add(x, y); int nValue(5); aValue[3] = 2; cObject.m_nValue = 4; pObject->m_nValue = 4; nValue++; nValue––; typeid(cClass).name(); const_cast<int*>(pnConstValue); dynamic_cast<Shape*>(pShape); reinterpret_cast<Class2>(cClass1); fValue = static_cast<float>(nValue); |

3 R->L |
+ - ++ –– ! ~ (type) sizeof & * new new[] delete delete[] |
Unary plus Unary minus Pre-increment Pre-decrement Logical NOT Bitwise NOT C-style cast Size in bytes Address of Dereference Dynamic memory allocation Dynamic array allocation Dynamic memory deletion Dynamic array deletion |
nValue = +5;M nValue = -1; ++nValue; ––nValue; if (!bValue) nFlags = ~nFlags; float fValue = (float)nValue; sizeof(int); address = &nValue; nValue = *pnValue; int *pnValue = new int; int *panValue = new int[5]; delete pnValue; delete[] panValue; |

4 L->R |
->* .* |
Member pointer selector Member object selector |
pObject->*pnValue = 24; cObject->.*pnValue = 24; |

5 L->R |
* / % |
Multiplication Division Modulus |
int nValue = 2 * 3; float fValue = 5.0 / 2.0; int nRemainder = 10 % 3; |

6 L->R |
+ - |
Addition Subtraction |
int nValue = 2 + 3; int nValue = 2 – 3; |

7 L->R |
<< >> |
Bitwise shift left Bitwise shift right |
int nFlags = 17 << 2; int nFlags = 17 >> 2; |

8 L->R |
< <= > >= |
Comparison less than Comparison less than or equals Comparison greater than Comparison greater than or equals |
if (x < y) if (x <= y) if (x > y) if (x >= y) |

9 L->R |
== != |
Equality Inequality |
if (x == y) if (x != y) |

10 L->R | & | Bitwise AND | nFlags = nFlags & 17; |

11 L->R | ^ | Bitwise XOR | nFlags = nFlags ^ 17; |

12 L->R | | | Bitwise OR | nFlags = nFlags | 17; |

13 L->R | && | Logical AND | if (bValue1 && bValue2) |

14 L->R | || | Logical OR | if (bValue1 || bValue2) |

15 L->R | ?: | Arithmetic if | return (x < y) ? true : false; |

16 R->L |
= *= /= %= += -= <<= >>= &= |= ^= |
Assignment Multiplication assignment Division assignment Modulus assignment Addition assignment Subtraction assignment Bitwise shift left assignment Bitwise shift right assignment Logical AND assingment Logical OR assignment Logical XOR assignment |
nValue = 5; nValue *= 5; fValue /= 5.0; nValue %= 5; nValue += 5; nValue -= 5; nFlags <<= 2; nFlags >>= 2; nFlags &= 17; nFlags |= 17; nFlags ^= 17; |

17 L->R | , | Comma operator | iii++, jjj++, kkk++; |

A few operators you should already recognize: +, -, *, /, (), =, <, >, <=, and >=. These arithmetic and relational operators have the same meaning in C++ as they do in every-day usage.

However, unless you have experience with another programming language, it’s likely the majority of the operators in this table will be incomprehensible to you at this point in time. That’s expected at this point. We’ll cover many of them in this chapter, and the rest will be introduced as there is a need for them.

The above table is primarily meant to be a reference chart that you can refer back to in the future to resolve any precedence or associativity questions you have.

3.2 — Arithmetic operators |

Index |

2.10 — Comprehensive quiz |

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Post-decrement and Pre-decrement are one minus/- short…

Thanks — HTML was converting –– into a single double-dash. HTML character encoding and programming sites don’t mix very well!

Call me a newb at this but I have no idea what Logical AND and Logical OR are.

i.e what would this mean?

Sorry, couldn’t find how to edit my previous post, I was also wondering what all the logical and what a bitwise shift is. Sorry if these questions are dumb but I want to fully understand each section before I move on incase it handicaps me later on.

Thanks

Go to google and type them in and they’ll probably explain it to you

I removed the paragraph that referenced logical AND and logical OR because it was confusing to introduce it at this point without an explanation of what those operators are. That information is covered again later in lesson 3.6.

You won’t be handicapped by not understanding what the majority of the operators are. They’ll all be explained as needed. Just keep reading. :)

Well, you’ve had a typo fault in here:

nValue = +5;M

You’ve accidently pressed the M there, as its right next to the semicolon. Just wanted to add that so you can fix it before people will encounter problems here.

Regards,

Extremo.

Is it a mistake that &=, |= and ^= are Logical AND, OR, XOR assignments, or they are bitwise?

Just a suggestion towards readability and clarity. The R->L and L->R could maybe be changed into R -> L and R <- L ?

just a suggestion; if you could make the chart in to an image file as well so people could save it and pull it up at any time it might be easier for referencing in the future.

shouldn’t the above code be:

???

if i am wrong explain to me please

btw, thanks for so good tutorials

really understandable since you use clear (and many) examples

Chapters from this tutorial are already blatantly copied by someone without even mentioning the source. Like here Precedence and associativity[^]. Note the site’s name too – “Learn C++ Programming” and try to find at least one his/her own word.

Hey Alex,

I cannot seem to find the exponent operator, ^. Am I missing it, or was it not included.

Thanks

Wintur

good tuts

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