Try It Yourself - SyntaxStudy Editor

HTML / CSS / JS

package main

import "fmt"

// Higher-order function: takes a function as an argument
func apply(nums []int, fn func(int) int) []int {
    out := make([]int, len(nums))
    for i, n := range nums {
        out[i] = fn(n)
    }
    return out
}

// Factory function returning a closure
func makeAdder(x int) func(int) int {
    return func(y int) int {
        return x + y
    }
}

// Closure capturing a mutable counter
func counter() (increment func(), get func() int) {
    n := 0
    increment = func() { n++ }
    get       = func() int { return n }
    return
}

func main() {
    double := func(n int) int { return n * 2 }
    nums   := []int{1, 2, 3, 4, 5}
    fmt.Println("doubled:", apply(nums, double))
    fmt.Println("squared:", apply(nums, func(n int) int { return n * n }))

add5 := makeAdder(5)
    fmt.Println("add5(3) =", add5(3))
    fmt.Println("add5(7) =", add5(7))

inc, get := counter()
    inc(); inc(); inc()
    fmt.Println("counter:", get()) // 3

// IIFE
    result := func(a, b int) int { return a + b }(10, 20)
    fmt.Println("IIFE result:", result)
}