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## listforeachif
6 years ago
### 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.
6 years ago
### Expected function and structure
```go
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) {
}
```
6 years ago
### Usage
Here is a possible program to test your function :
```go
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 :
```console
$ go run .
1->hello->3->there->23->!->54->nil
--------function applied--------
1
3
23
54
--------function applied--------
1->2->3->2->23->2->54->nil
$
```