# Objective-C Operators

An operator is a symbol that tells the compiler to perform specific mathematical or logical manipulations. Objective-C language is rich in built-in operators and provides following types of operators:

Arithmetic Operators

Relational Operators

Logical Operators

Bitwise Operators

Assignment Operators

Misc Operators

This tutorial will explain the arithmetic, relational, logical, bitwise, assignment and other operators one by one.

## Arithmetic Operators

Following table shows all the arithmetic operators supported by Objective-C language. Assume variable **A** holds 10 and variable **B** holds 20, then:

Operator | Description | Example |
---|---|---|

+ | Adds two operands | A + B will give 30 |

- | Subtracts second operand from the first | A - B will give -10 |

* | Multiplies both operands | A * B will give 200 |

/ | Divides numerator by denominator | B / A will give 2 |

% | Modulus Operator and remainder of after an integer division | B % A will give 0 |

++ | Increment operator increases integer value by one | A++ will give 11 |

-- | Decrement operator decreases integer value by one | A-- will give 9 |

## Relational Operators

Following table shows all the relational operators supported by Objective-C language. Assume variable **A** holds 10 and variable **B** holds 20, then:

Operator | Description | Example |
---|---|---|

== | Checks if the values of two operands are equal or not; if yes, then condition becomes true. | (A == B) is not true. |

!= | Checks if the values of two operands are equal or not; if values are not equal, then condition becomes true. | (A != B) is true. |

> | Checks if the value of left operand is greater than the value of right operand; if yes, then condition becomes true. | (A > B) is not true. |

< | Checks if the value of left operand is less than the value of right operand; if yes, then condition becomes true. | (A < B) is true. |

>= | Checks if the value of left operand is greater than or equal to the value of right operand; if yes, then condition becomes true. | (A >= B) is not true. |

<= | Checks if the value of left operand is less than or equal to the value of right operand; if yes, then condition becomes true. | (A <= B) is true. |

## Logical Operators

Following table shows all the logical operators supported by Objective-C language. Assume variable **A** holds 1 and variable **B** holds 0, then:

Operator | Description | Example |
---|---|---|

&& | Called Logical AND operator. If both the operands are non zero then condition becomes true. | (A && B) is false. |

|| | Called Logical OR Operator. If any of the two operands is non zero then condition becomes true. | (A || B) is true. |

! | Called Logical NOT Operator. Use to reverses the logical state of its operand. If a condition is true, then Logical NOT operator will make false. | !(A && B) is true. |

## Bitwise Operators

Bitwise operator works on bits and perform bit by bit operation. The truth tables for &, |, and ^ are as follows:

p | q | p & q | p | q | p ^ q |
---|---|---|---|---|

0 | 0 | 0 | 0 | 0 |

0 | 1 | 0 | 1 | 1 |

1 | 1 | 1 | 1 | 0 |

1 | 0 | 0 | 1 | 1 |

Assume if A = 60; and B = 13; now in binary format they will be as follows:

A = 0011 1100

B = 0000 1101

-----------------

A&B = 0000 1100

A|B = 0011 1101

A^B = 0011 0001

~A = 1100 0011

The Bitwise operators supported by Objective-C language are listed in the following table. Assume variable A holds 60 and variable B holds 13 then:

Operator | Description | Example |
---|---|---|

& | Binary AND Operator copies a bit to the result if it exists in both operands. | (A & B) will give 12, which is 0000 1100 |

| | Binary OR Operator copies a bit if it exists in either operand. | (A | B) will give 61, which is 0011 1101 |

^ | Binary XOR Operator copies the bit if it is set in one operand but not both. | (A ^ B) will give 49, which is 0011 0001 |

~ | Binary Ones Complement Operator is unary and has the effect of 'flipping' bits. | (~A ) will give -61, which is 1100 0011 in 2's complement form. |

<< | Binary Left Shift Operator. The left operands value is moved left by the number of bits specified by the right operand. | A << 2 will give 240, which is 1111 0000 |

>> | Binary Right Shift Operator. The left operands value is moved right by the number of bits specified by the right operand. | A >> 2 will give 15, which is 0000 1111 |

## Assignment Operators

There are following assignment operators supported by Objective-C language:

Operator | Description | Example |
---|---|---|

= | Simple assignment operator, Assigns values from right side operands to left side operand | C = A + B will assign value of A + B into C |

+= | Add AND assignment operator, It adds right operand to the left operand and assigns the result to left operand | C += A is equivalent to C = C + A |

-= | Subtract AND assignment operator, It subtracts right operand from the left operand and assigns the result to left operand | C -= A is equivalent to C = C - A |

*= | Multiply AND assignment operator, It multiplies right operand with the left operand and assigns the result to left operand | C *= A is equivalent to C = C * A |

/= | Divide AND assignment operator, It divides left operand with the right operand and assigns the result to left operand | C /= A is equivalent to C = C / A |

%= | Modulus AND assignment operator, It takes modulus using two operands and assigns the result to left operand | C %= A is equivalent to C = C % A |

<<= | Left shift AND assignment operator | C <<= 2 is same as C = C << 2 |

>>= | Right shift AND assignment operator | C >>= 2 is same as C = C >> 2 |

&= | Bitwise AND assignment operator | C &= 2 is same as C = C & 2 |

^= | bitwise exclusive OR and assignment operator | C ^= 2 is same as C = C ^ 2 |

|= | bitwise inclusive OR and assignment operator | C |= 2 is same as C = C | 2 |

## Misc Operators ↦ sizeof & ternary

There are few other important operators including **sizeof** and **? :** supported by Objective-C Language.

Operator | Description | Example |
---|---|---|

sizeof() | Returns the size of an variable. | sizeof(a), where a is integer, will return 4. |

& | Returns the address of an variable. | &a; will give actual address of the variable. |

* | Pointer to a variable. | *a; will pointer to a variable. |

? : | Conditional Expression | If Condition is true ? Then value X : Otherwise value Y |

## Operators Precedence in Objective-C

Operator precedence determines the grouping of terms in an expression. This affects how an expression is evaluated. Certain operators have higher precedence than others; for example, the multiplication operator has higher precedence than the addition operator:

For example, x = 7 + 3 * 2; here, x is assigned 13, not 20 because operator * has higher precedence than +, so it first gets multiplied with 3*2 and then adds into 7.

Here, operators with the highest precedence appear at the top of the table, those with the lowest appear at the bottom. Within an expression, higher precedence operators will be evaluated first.

Category | Operator | Associativity |
---|---|---|

Postfix | () [] -> . ++ - - | Left to right |

Unary | + - ! ~ ++ - - (type)* & sizeof | Right to left |

Multiplicative | * / % | Left to right |

Additive | + - | Left to right |

Shift | << >> | Left to right |

Relational | < <= > >= | Left to right |

Equality | == != | Left to right |

Bitwise XOR | ^ | Left to right |

Bitwise OR | | | Left to right |

Logical AND | && | Left to right |

Logical OR | || | Left to right |

Conditional | ?: | Right to left |

Assignment | = += -= *= /= %=>>= <<= &= ^= |= | Right to left |

Comma | , | Left to right |