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Basic Syntax and Structure

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In this section, we will cover the fundamental syntax and structure of Go programs. Understanding these basics is crucial for writing efficient and readable Go code.

Key Concepts

  1. Package Declaration
  2. Importing Packages
  3. Functions
  4. Variables
  5. Constants
  6. Comments

  1. Package Declaration

Every Go program starts with a package declaration. The main package is special because it defines a standalone executable program.

package main

  1. Importing Packages

To use functions from other packages, you need to import them. The fmt package is commonly used for formatted I/O.

import "fmt"

  1. Functions

The main function is the entry point of a Go program. Other functions can be defined to organize code.

func main() {
    fmt.Println("Hello, World!")
}

Example: Defining and Calling a Function

package main

import "fmt"

func main() {
    greet("Alice")
}

func greet(name string) {
    fmt.Printf("Hello, %s!\n", name)
}

Explanation:

  • func main() defines the main function.
  • greet(name string) defines a function that takes a string argument.

  1. Variables

Variables in Go are declared using the var keyword or the shorthand := syntax.

Example: Variable Declaration

package main

import "fmt"

func main() {
    var age int = 30
    name := "Alice"
    fmt.Printf("%s is %d years old.\n", name, age)
}

Explanation:

  • var age int = 30 declares a variable with explicit type.
  • name := "Alice" uses shorthand syntax for type inference.

  1. Constants

Constants are declared using the const keyword and cannot be changed after declaration.

Example: Constant Declaration

package main

import "fmt"

func main() {
    const pi = 3.14
    fmt.Println("The value of pi is", pi)
}

Explanation:

  • const pi = 3.14 declares a constant.

  1. Comments

Comments are used to explain code and are ignored by the compiler.

Example: Comments

package main

import "fmt"

func main() {
    // This is a single-line comment
    fmt.Println("Hello, World!") // This comment is at the end of a line

    /*
       This is a multi-line comment
       It can span multiple lines
    */
}

Practical Exercise

Exercise 1: Basic Program

Write a Go program that declares a variable for your name and age, and then prints a greeting message.

Solution:

package main

import "fmt"

func main() {
    name := "John"
    age := 25
    fmt.Printf("Hello, my name is %s and I am %d years old.\n", name, age)
}

Exercise 2: Using Functions

Write a Go program that defines a function to calculate the square of a number and prints the result.

Solution:

package main

import "fmt"

func main() {
    number := 4
    result := square(number)
    fmt.Printf("The square of %d is %d.\n", number, result)
}

func square(n int) int {
    return n * n
}

Common Mistakes and Tips

  • Missing Package Declaration: Always start your Go files with a package declaration.
  • Unused Imports: Go will not compile if there are unused imports. Remove any imports that are not being used.
  • Variable Shadowing: Be careful not to redeclare variables in the same scope, which can lead to unexpected behavior.

Conclusion

In this section, we covered the basic syntax and structure of Go programs, including package declaration, importing packages, defining functions, declaring variables and constants, and using comments. These fundamentals are essential for writing any Go program. In the next module, we will dive deeper into basic concepts such as variables, data types, and control structures.

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