Update strlenprog.en.md

subjects/strlenprog.en.md

@@ -1,19 +1,52 @@
 ## strlenprog
 
+##**WARNING! VERY IMPORTANT!**
+
+For this exercise a function will be tested **with the exam own main**. However the student **still needs** to submit a structured program:
+
+This means that:
+
+- The package needs to be named `package main`.
+- The submitted code needs one declared function main(```func main()```) even if empty.
+- The function main declared needs to **also pass** the `Restrictions Checker`(illegal functions tester). It is advised for the student to just empty the function main after its own testings are done.
+- Every other rules are obviously the same than for a `program`.
+
 ### Instructions
 
--   Write a program that counts the characters of a `string` and that returns that value.
+-   Write a function that counts the characters of a `string` and that returns that count.
 
--   If the program receives more than one or no arguments it must not print anything.
+### Expected function
+
+```go
+func StrLen(str string) int {
+
+}
+```
+
+### Usage
+
+Here is a possible [program](TODO-LINK) to test your function :
+
+```go
+package main
+
+import (
+	"fmt"
+	piscine ".."
+)
+
+func main() {
+	str := "Hello World!"
+	nb := piscine.StrLen(str)
+	fmt.Println(nb)
+}
+```
 
-### Expected output :
+And its output :
 
 ```console
-student@ubuntu:~/piscine-go/strlenprog$ go build
-student@ubuntu:~/piscine-go/strlenprog$ ./strlenprog "hello" | cat -e
-5$
-student@ubuntu:~/piscine-go/strlenprog$ ./strlenprog
-student@ubuntu:~/piscine-go/strlenprog$
-student@ubuntu:~/piscine-go/strlenprog$ ./strlenprog "hello" "how are you"
-student@ubuntu:~/piscine-go/strlenprog$
+student@ubuntu:~/piscine-go/test$ go build
+student@ubuntu:~/piscine-go/test$ ./test
+12
+student@ubuntu:~/piscine-go/test$
 ```