Operators

## Learning Objectives - Master arithmetic operators - Understand comparison operators - Learn logical operators - Work with bitwise operators - Understand operator precedence ## Arithmetic Operators ### Basic Operations ```go a, b := 10, 3 fmt.Println(a + b) // 13 (addition) fmt.Println(a - b) // 7 (subtraction) fmt.Println(a * b) // 30 (multiplication) fmt.Println(a / b) // 3 (integer division) fmt.Println(a % b) // 1 (modulus/remainder) ``` ### Division Behavior ```go // Integer division truncates toward zero fmt.Println(10 / 3) // 3, not 3.333... // For floating-point division fmt.Println(10.0 / 3.0) // 3.333... ``` ### Increment/Decrement ```go x := 5 x++ // x = 6 (equivalent to x += 1) x-- // x = 5 (equivalent to x -= 1) // Pre/post behavior is the same - no value returned fmt.Println(x) // 5 ``` ### Compound Assignment ```go x := 10 x += 5 // x = 15 x -= 3 // x = 12 x *= 2 // x = 24 x /= 4 // x = 6 x %= 5 // x = 1 ``` ## Comparison Operators ### Relational Operators ```go a, b := 5, 10 fmt.Println(a == b) // false (equal) fmt.Println(a != b) // true (not equal) fmt.Println(a < b) // true (less than) fmt.Println(a > b) // false (greater than) fmt.Println(a <= b) // true (less or equal) fmt.Println(a >= b) // false (greater or equal) ``` ### Important Note ```go // = is assignment // == is comparison x := 5 if x == 5 { // Correct: compares x to 5 fmt.Println("x is 5") } ``` ## Logical Operators ### AND, OR, NOT ```go a, b := true, false fmt.Println(a && b) // false (AND - both must be true) fmt.Println(a || b) // true (OR - one must be true) fmt.Println(!a) // false (NOT - inverts) ``` ### Short-Circuit Evaluation ```go x := 0 // && stops if first is false if x != 0 && y/x > 2 { // Safe - won't divide by zero fmt.Println("safe") } // || stops if first is true if obj == nil || obj.isValid() { // Safe - won't call on nil fmt.Println("safe") } ``` ### Truth Table | A | B | A && B | A \|\| B | !A | |---|---|--------|----------|-----| | true | true | true | true | false | | true | false | false | true | false | | false | true | false | true | true | | false | false | false | false | true | ## Bitwise Operators ### Binary Operations ```go a, b := 5, 3 // 101 and 011 in binary fmt.Println(a & b) // 1 (AND: 101 & 011 = 001) fmt.Println(a | b) // 7 (OR: 101 | 011 = 111) fmt.Println(a ^ b) // 6 (XOR: 101 ^ 011 = 110) fmt.Println(^a) // -6 (NOT: ^101 = ...010 = -6) fmt.Println(a << 1) // 10 (left shift: 101 << = 1010) fmt.Println(a >> 1) // 2 (right shift: 101 >> = 10) ``` ### Bitwise Assignment ```go x := 10 x &= 3 // x = x & 3 x |= 3 // x = x | 3 x ^= 3 // x = x ^ 3 x <<= 2 // x = x << 2 x >>= 1 // x = x >> 1 ``` ### Common Uses ```go // Check if bit is set flags := 0b1010 // 10 in decimal if flags & 0b1000 != 0 { fmt.Println("Bit 3 is set") } // Set a bit flags = flags | 0b0001 // Toggle a bit flags = flags ^ 0b0100 // Clear a bit flags = flags &^ 0b0100 ``` ## Address Operators ### Pointer Operations ```go x := 10 p := &x // Get address of x fmt.Println(p) // Memory address (e.g., 0xc00000a008) fmt.Println(*p) // 10 (dereference) *p = 20 // Change value through pointer fmt.Println(x) // 20 ``` ### New Operator ```go p := new(int) // Creates pointer to int with zero value fmt.Println(*p) // 0 ``` ## Channel Operators ### Channel Creation and Operations ```go ch := make(chan int) // Send and receive ch <- 10 // Send 10 to channel value := <-ch // Receive from channel ``` ## Operator Precedence ### Highest to Lowest | Priority | Operators | |----------|-------------------| | 1 | `*`, `/`, `%`, `<<`, `>>`, `&`, `&^` | | 2 | `+`, `-`, `\|`, `^` | | 3 | `==`, `!=`, `<`, `<=`, `>`, `>=` | | 4 | `<-` (channel) | | 5 | `&&` | | 6 | `\|\|` | ### Use Parentheses ```go // Clear precedence if (a > b) && (c < d) { fmt.Println("Both conditions true") } // Same result, less clear if a > b && c < d { fmt.Println("Both conditions true") } ``` ## Type Assertion Operators ### Type Switch ```go var i interface{} = "hello" switch v := i.(type) { case int: fmt.Printf("Integer: %d\n", v) case string: fmt.Printf("String: %s\n", v) default: fmt.Printf("Unknown type\n") } ``` ### Type Assertion ```go var i interface{} = "hello" s := i.(string) // Panics if not string s, ok := i.(string) // Safe: ok is false if not string ``` ## Summary - Arithmetic: `+`, `-`, `*`, `/`, `%` - Increment/Decrement: `++`, `--` - Comparison: `==`, `!=`, `<`, `>`, `<=`, `>=` - Logical: `&&`, `||`, `!` - Bitwise: `&`, `|`, `^`, `~`, `<<`, `>>` - Assignment: `=`, `+=`, `-=`, etc. - Pointer: `&` (address), `*` (dereference) - Channel: `<-` (send/receive) - Use parentheses to clarify precedence