Function parameters in Go - Cheat Sheet & Quick Revision

Recall & Review

beginner

What are function parameters in Go?

Function parameters are variables listed in a function's definition. They receive values when the function is called, allowing the function to use those values inside its code.

beginner

How do you define multiple parameters of the same type in Go?

You can list multiple parameter names followed by a single type. For example: func add(x, y int) int means both x and y are integers.

beginner

What happens if you call a function without providing all parameters?

Go requires all parameters to be provided when calling a function. Missing parameters cause a compile-time error.

intermediate

Can function parameters have default values in Go?

No, Go does not support default parameter values. You must provide all arguments when calling the function.

intermediate

What is a variadic parameter in Go?

A variadic parameter lets a function accept zero or more arguments of a specified type. It is declared with ... before the type, like func sum(nums ...int).

How do you declare two integer parameters named a and b in a Go function?

A func example(a, b int)

B func example(int a, int b)

C func example(a int, b int)

D func example(a int b int)

In Go, you list parameter names followed by their type. So 'a, b int' means both are integers. Alternatively, you can specify each parameter with its type separately as in 'a int, b int'.

What happens if you call a Go function with fewer arguments than parameters?

A Compile-time error

B Function uses default values

C Function ignores missing parameters

D Runtime error

Go requires all parameters to be provided. Missing arguments cause a compile-time error.

Which symbol is used to declare a variadic parameter in Go?

A ...

B *

C &

D $

The '...' before a type declares a variadic parameter that accepts multiple arguments.

Can Go functions have parameters with default values?

A Yes, using the 'default' keyword

B Yes, by assigning values in the function signature

C No, Go does not support default parameter values

D Only for string parameters

Go requires all arguments to be passed explicitly; it does not support default parameter values.

What is the correct way to define a function that takes any number of integers in Go?

A func sum(nums *int)

B func sum(nums ...int)

C func sum(...nums int)

D func sum(nums int[])

The '...int' syntax declares a variadic parameter accepting zero or more integers.

Explain how function parameters work in Go and how you declare multiple parameters of the same type.

Think about how you list names and types in the function signature.

Describe what a variadic parameter is in Go and how it differs from regular parameters.

It's like a function that can take many values of the same type.

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