If Control Statements

Key observations:

1. Parentheses around conditional expressions are optional and conventionally omitted
2. A short variable declaration can precede the condition, separated by a semicolon; variables declared this way are scoped to the entire if-else chain
3. Prefer concise conditional expressions
4. Go lacks a ternary conditional operator (e.g., a > b ? 1 : 0)

package main

import "fmt"

func main() {
	threshold := 12
	if score := 12; score < threshold {
		fmt.Println("score below threshold")
	} else if score == threshold {
		fmt.Println("score matches threshold")
	} else {
		fmt.Println("score exceeds threshold")
	}
}

Switch Control Statements

fallthrough forces execution to continue into the immediately following case block, skipping its condition check. It does not cascade through all subsequent cases.

package main

import "fmt"

func main() {
	switch response := 'Y'; response {
	case 'y', 'Y':
		fmt.Println("affirmative")
		fallthrough
	case 'n', 'N':
		fmt.Println("binary choice processed")
	case 'a', 'A':
		fmt.Println("all selected")
	}
}

Output:

affirmative
binary choice processed

The default case can appear anywhere in the switch block; placement does not alter execution order.

switch token := 'z'; token {
default:
	fmt.Println("unrecognized token")
case 'y', 'Y':
	fmt.Println("affirmative")
	fallthrough
case 'n', 'N':
	fmt.Println("binary choice processed")
}

Output:

unrecognized token

To Loop Control Structures

Go provides only one loop construct: for, which supports multiple iteration patterns.

Range-Based Iteration Over Arrays

func iterateFixedArray() {
	numbers := [5]int{7, 14, 21, 28, 35}
	for index := range numbers {
		fmt.Println(numbers[index])
	}
}

Range-Based Iteration Over Slices

func iterateSubslice() {
	base := [...]int{9, 18, 27, 36, 45, 54}
	selected := base[3:]
	for _, val := range selected {
		fmt.Println(val)
	}
}

func iterateMakeSlice() {
	scores := make([]int, 4)
	scores[0] = 89
	scores[1] = 92
	scores[3] = 77
	for idx, s := range scores {
		fmt.Printf("Position %d: %d\n", idx, s)
	}
}

Output for iterateMakeSlice():

Position 0: 89
Position 1: 92
Position 2: 0
Position 3: 77

Range-Based Iteration Over Maps

func iterateStudentScores() {
	gradeBook := map[string]int{"Charlie": 85, "Diana": 91, "Evan": 78}

	// Iterate over keys only
	for name := range gradeBook {
		fmt.Println(name)
	}

	// Iterate over values only
	for _, score := range gradeBook {
		fmt.Println(score)
	}

	// Iterate over key-value pairs
	for n, s := range gradeBook {
		fmt.Printf("%s: %d\n", n, s)
	}
}