Go - Functions as Values

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Functions as Values

Go programming language provides the flexibility to create functions on the fly and use them as values. In the following example, we've initialized a variable with a function definition. Purpose of this function variable is just to use inbuilt math.sqrt() function.

Example

For example −

 package main import ("fmt" "math") func main(){ /* declare a function variable */ getSquareRoot := func(x float64) float64 { return math.Sqrt(x) } /* use the function */ fmt.Println(getSquareRoot(9)) } 

When the above code is compiled and executed, it produces the following result −

 3 

In Go language, the functions can be assigned to variables, passed as arguments to other functions, or returned as values from functions. Let's understand each concept in detail.

Assigning a Function to a Variable

Go language allows you to assign a function directly to a variable. The function should have a return type.

Example

 package main import "fmt" // Function func addTwoNumbers(a int, b int) int { return a + b } func main() { // Assign the function to a variable sum := addTwoNumbers // Here, we are calling the function // using the variable result := sum(100, 200) fmt.Println("Sum:", result) } 

When the above code is compiled and executed, it produces the following result −

 Sum: 300 

Passing a Function as an Argument

You can pass a function to a function as an argument; you just need to use the function declaration as an argument.

Example

 package main import "fmt" // Passing a Function as an Argument func calculation(x int, y int, op func(int, int) int) int { return op(x, y) } func multiplyNumbers(x int, y int) int { return x * y } func main() { result := calculation (2, 5, multiplyNumbers) fmt.Println("Result:", result) } 

When the above code is compiled and executed, it produces the following result −

 Result: 10 

Returning a Function as a Value

A function can also return a function as a value in the Go language. It is useful when you want to return an expression calculated by creating any function.

Example

 package main import "fmt" // Returning a Function as a Value func calculation(factor int) func(int) int { return func(value int) int { return factor * value } } func main() { multiplyByTwo := calculation(2) result := multiplyByTwo(20) fmt.Println("Result:", result) } 

When the above code is compiled and executed, it produces the following result −

 Result: 40