What are the common uses of golang functional programming?

Go language supports functional programming and provides built-in functional tools such as map, filter, reduce, etc., allowing the use of stateless functions and immutable data. Higher-order functions allow functions to accept or return other functions, such as the sort.Slice function. Closure nested functions can access the scope of the enclosing function, creating reusable and ful functions. In addition, the Go language supports higher-order functions and closures for building flexible and reusable code.

Common usage of functional programming in Go language

Functional programming is a programming paradigm that emphasizes the use of stateless functions and immutable data, while Not mutable state and side effects. The Go language supports functional programming and provides some useful built-in functions and mechanisms to help you implement functional code.

Built-in functional tools

Go provides some built-in functional tools that can help you manipulate collections, transform data, and perform other common functional tasks. These tools include:

• #map: Maps a function to a collection and returns a new collection.
• filter: Filter the collection to only retain elements that meet certain conditions.
• reduce: Aggregate a collection to combine elements into a single value using the provided function.
• take: Gets the specified number of elements from the end of the collection.
• skip: Skip the specified number of elements from the beginning of the collection.

Higher-order functions

Higher-order functions accept other functions as input or return functions as output. Go supports higher-order functions, which allows you to build reusable and flexible code.

A common example is the sort.Slice function, which takes a comparison function and sorts the slice it is passed:

package main

import (
    "fmt"
    "sort"
)

func compareInt(a, b int) int {
    if a < b {
        return -1
    }
    if a > b {
        return 1
    }
    return 0
}

func main() {
    nums := []int{3, 1, 7, 5, 9}
    sort.Slice(nums, compareInt)
    fmt.Println(nums)
}

Closure

A closure is a nested function that has access to the scope of its enclosing function, even if it has returned. This allows you to create stateful, reusable functions.

A common example is the funcFilter function, which returns a new function that filters a collection based on a given predicate:

package main

import "fmt"

func main() {
    nums := []int{3, 1, 7, 5, 9}
    funcFilter := func(fn func(int) bool) func([]int) []int {
        return func(s []int) []int {
            var r []int
            for _, n := range s {
                if fn(n) {
                    r = append(r, n)
                }
            }
            return r
        }
    }
    filterOdd := funcFilter(func(n int) bool { return n%2 != 0 })
    fmt.Println(filterOdd(nums))
}

Practical case

The following is an example of using functional programming to calculate word frequencies:

package main

import (
    "fmt"
    "strings"
)

func main() {
    text := "The quick brown fox jumped over the lazy dog"
    words := strings.Fields(text)

    wordFrequencies := make(map[string]int)
    for _, w := range words {
        if _, ok := wordFrequencies[w]; !ok {
            wordFrequencies[w] = 0
        }
        wordFrequencies[w]++
    }

    for w, f := range wordFrequencies {
        fmt.Printf("%s: %d\n", w, f)
    }
}

In this example, we iterate through the collection of words and store the frequency of each word in a map. We use map and range to implement functional set operations.

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