public/subjects/listforeachif.en.md

listforeachif

Instructions

Write a function ListForEachIf that applies a function given as argument to the data within some of the nodes of the list l.

• This function receives two functions:

  • f is a function that is applied to the node.

  • cond is a function that returns a boolean and it will be used to determine if the function f should be applied to the node.

• The function given as argument must have a pointer *NodeL as argument.

Expected function and structure

type NodeL struct {
	Data interface{}
	Next *NodeL
}

type List struct {
	Head *NodeL
	Tail *NodeL
}

func IsPositive_node(node *NodeL) bool {
	switch node.Data.(type) {
	case int, float32, float64, byte:
		return node.Data.(int) > 0
	case string, rune:
		return false
	}
	return false
}

func IsNegative_node(node *NodeL) bool {
	switch node.Data.(type) {
	case int, float32, float64, byte:
		return node.Data.(int) < 0
	case string, rune:
		return false
	}
	return false
}

func IsNotNumeric_node(node *NodeL) bool {
	switch node.Data.(type) {
	case int, float32, float64, byte:
		return false
	case string, rune:
		return true
	}
	return true
}

func ListForEachIf(l *List, f func(*NodeL), cond func(*NodeL) bool) {

}

Usage

Here is a possible program to test your function :

package main

import (
	piscine ".."
	"fmt"
)

func PrintElem(node *piscine.NodeL) {
	fmt.Println(node.Data)
}

func StringToInt(node *piscine.NodeL) {
	node.Data = 2
}

func PrintList(l *piscine.List) {
	it := l.Head
	for it != nil {
		fmt.Print(it.Data, "->")
		it = it.Next
	}
	fmt.Print("nil","\n")
}

func main() {
	link := &piscine.List{}

	piscine.ListPushBack(link, 1)
	piscine.ListPushBack(link, "hello")
	piscine.ListPushBack(link, 3)
	piscine.ListPushBack(link, "there")
	piscine.ListPushBack(link, 23)
	piscine.ListPushBack(link, "!")
	piscine.ListPushBack(link, 54)

	PrintList(link)

	fmt.Println("--------function applied--------")
	piscine.ListForEachIf(link, PrintElem, piscine.IsPositive_node)

	piscine.ListForEachIf(link, StringToInt, piscine.IsNotNumeric_node)

	fmt.Println("--------function applied--------")
	PrintList(link)

	fmt.Println()
}

And its output :

student@ubuntu:~/[[ROOT]]/test$ go build
student@ubuntu:~/[[ROOT]]/test$ ./test
1->hello->3->there->23->!->54->nil
--------function applied--------
1
3
23
54
--------function applied--------
1->2->3->2->23->2->54->nil

student@ubuntu:~/[[ROOT]]/test$
student@ubuntu:~/[[ROOT]]/test$