## listpushback
### Instructions
Write a function `ListForEachIf` that applies a function given as argument to the information within some links of the list.
- For this you will have to create a function `CompStr` , that returns a `bool` , to compare each elemente of the linked list, to see if it is a string, and than apply the function in the argument of `ListForEachIf` .
- The function given as argument as to have a pointer as argument: `l *list` .
- Use pointers wen ever you can.
### Expected function and structure
```go
type node struct {
data interface{}
next *node
}
type list struct {
head *node
tail *node
}
func CompStr(l *list) bool {
}
func ListForEachIf(l *list, f func(l *list), comp func(l *list) bool) {
}
```
### Usage
Here is a possible [program ](TODO-LINK ) to test your function :
```go
package main
import (
"fmt"
piscine ".."
)
func PrintElem(l *list) {
fmt.Println(l.head.data)
}
func StringToInt(l *list) {
count := 1
l.head.data = count
}
func PrintList(l *list) {
m := l.head
for m != nil {
fmt.Print(m.data, " -> ")
m = m.next
}
fmt.Print(l.tail)
}
func main() {
link := & 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)
PrintAllList(link)
fmt.Println()
fmt.Println("--------function applied--------")
piscine.ListForEachIf(link, PrintElem, CompStr)
piscine.ListForEachIf(link, StringToInt, CompStr)
fmt.Println("--------function applied--------")
PrintAllList(link)
fmt.Println()
}
```
And its output :
```console
student@ubuntu:~/piscine/test$ go build
student@ubuntu:~/piscine/test$ ./test
1 -> hello -> 3 -> there -> 23 -> ! -> 54 -> < nil >
--------function applied--------
hello
there
!
--------function applied--------
1 -> 1 -> 3 -> 1 -> 23 -> 1 -> 54 -> < nil >
student@ubuntu:~/piscine/test$
```
