Function parameters in Go - Mini Project: Build & Apply

Function parameters

📖 Scenario: You are creating a simple calculator program in Go. The calculator will add two numbers provided by the user.

🎯 Goal: Build a Go program that defines a function with parameters to add two numbers and then prints the result.

📋 What You'll Learn

Create a function named add that takes two int parameters named a and b.

The add function should return the sum of a and b.

Call the add function with two integer arguments.

Print the result of the add function call.

💡 Why This Matters

🌍 Real World

Functions with parameters let you reuse code for different inputs, like calculators or data processors.

💼 Career

Understanding function parameters is essential for writing clean, reusable code in any software development job.

1

Create the main function

Write the main function with an empty body.

Go

func main() {
    // Your code here
}

Hint

The main function is the starting point of a Go program.

2

Define the add function with parameters

Define a function named add that takes two int parameters named a and b, and returns an int.

Go

package main

func main() {
    
}

// Define the add function here
// Your code here

Hint

Use func add(a int, b int) int to define the function with parameters and return type.

3

Call the add function with arguments

Inside the main function, call the add function with arguments 5 and 3, and store the result in a variable named sum.

Go

package main

func main() {
    // Call add with 5 and 3 and store in sum
    // Your code here
}

func add(a int, b int) int {
    return a + b
}

Hint

Use sum := add(5, 3) to call the function and save the result.

4

Print the result

Add a fmt.Println statement inside main to print the value of sum. Remember to import the fmt package.

Go

package main

import "fmt"

func main() {
    sum := add(5, 3)
    // Print sum here
    // Your code here
}

func add(a int, b int) int {
    return a + b
}

Hint

Use fmt.Println(sum) to print the sum. Don't forget to import fmt.

Practice

1. What is the purpose of function parameters in Go?

easy

A. To print output from a function

B. To create new functions automatically

C. To stop a function from running

D. To send data into functions so they can use it

Solution

1. Step 1: Understand what parameters do

   Parameters let you give information to a function when you call it.

2. Step 2: Identify the correct purpose

   Sending data into functions makes them flexible and reusable with different inputs.

3. Final Answer:

   To send data into functions so they can use it -> Option D

4. Quick Check:

   Function parameters = send data into functions [OK]

Hint: Parameters pass data into functions for reuse [OK]

Common Mistakes:

• Thinking parameters create functions
• Confusing parameters with output
• Believing parameters stop function execution

2. Which of the following is the correct way to declare a function with two integer parameters in Go?

easy

A. func add(a, b int) int {}

B. func add(a int, b) int {}

C. func add(int a, int b) int {}

D. func add(a int b int) int {}

Solution

1. Step 1: Review Go function parameter syntax

   In Go, you can group parameters of the same type like a, b int.

2. Step 2: Identify correct syntax

   func add(a, b int) int {} groups same type parameters correctly. func add(a int, b) int {} misses type for b. func add(int a, int b) int {} places types before names. func add(a int b int) int {} lacks commas.

3. Final Answer:

   func add(a, b int) int {} -> Option A

4. Quick Check:

   Group same type params: a, b int [OK]

Hint: Group same type params with commas before type [OK]

Common Mistakes:

• Writing types before variable names (like C)
• Missing commas between parameters (like D)
• Forgetting type for second parameter (like B)

3. What will be the output of this Go program?

package main
import "fmt"
func greet(name string) {
    fmt.Println("Hello, " + name)
}
func main() {
    greet("Alice")
}

medium

A. Hello,

B. Hello, Alice

C. Hello, name

D. Compilation error

Solution

1. Step 1: Understand function call with parameter

   The function greet takes a string parameter name and prints "Hello, " plus that name.

2. Step 2: Check the argument passed

   In main, greet("Alice") is called, so name is "Alice".

3. Final Answer:

   Hello, Alice -> Option B

4. Quick Check:

   Function prints "Hello, " + argument [OK]

Hint: Function prints greeting plus passed name [OK]

Common Mistakes:

• Confusing parameter name with string literal
• Expecting no output
• Thinking it causes error without return

4. Identify the error in this Go function declaration:

func multiply(a int, b int) int {
    return a * b
}

func main() {
    result := multiply(3)
    fmt.Println(result)
}

medium

A. Function multiply called with wrong number of arguments

B. Missing import for fmt package

C. Return type missing in multiply function

D. Variable result not declared

Solution

1. Step 1: Check function call arguments

   The function multiply requires two int parameters, but it is called with only one argument 3.

2. Step 2: Identify the error

   This causes a compile-time error due to wrong number of arguments.

3. Final Answer:

   Function multiply called with wrong number of arguments -> Option A

4. Quick Check:

   Function call args must match parameters [OK]

Hint: Count arguments to match parameters exactly [OK]

Common Mistakes:

• Ignoring missing import for fmt (not shown here)
• Thinking return type is missing
• Assuming variable declaration error

5. Given this Go function:

func sumAndProduct(a, b int) (int, int) {
    return a + b, a * b
}

func main() {
    s, p := sumAndProduct(4, 5)
    fmt.Println(s, p)
}

What will be the output when the program runs?

hard

A. 20 9

B. 9

C. 9 20

D. Compilation error due to missing return

Solution

1. Step 1: Understand multiple return values

   The function sumAndProduct returns two integers: sum and product of a and b.

2. Step 2: Check values for inputs 4 and 5

   Sum is 4 + 5 = 9, product is 4 * 5 = 20. These are assigned to s and p.

3. Step 3: Print output

   fmt.Println(s, p) prints "9 20".

4. Final Answer:

   9 20 -> Option C

5. Quick Check:

   Multiple returns print sum then product [OK]

Hint: Multiple returns unpacked in order [OK]

Common Mistakes:

• Swapping sum and product values
• Expecting single return value
• Thinking missing return error