Update of doop

Added details and corrected unclearness

subjects/doop.en.md

@@ -14,9 +14,11 @@ In case of an invalid entry the programs prints `0`.
 
 In case of an invalid number of arguments the program prints nothing.
 
+The program has to handle the modulo and division by 0 as shown on the output examples below. 
+
 `fmt.Print` is authorized.
 
-### Usage
+Examples of outputs :
 
 ```console
 student@ubuntu:~/piscine/test$ go build doop.go
@@ -29,10 +31,10 @@ student@ubuntu:~/piscine/test$ ./doop 1 p 1
 0
 student@ubuntu:~/piscine/test$ ./doop 1 + 1
 2
-student@ubuntu:~/piscine/test$ ./doop 1 / 0
-No division by 0
-student@ubuntu:~/piscine/test$ ./doop 1 % 0
-No modulo by 0
-student@ubuntu:~/piscine/test$ ./doop 1 * 1
+student@ubuntu:~/piscine/test$ ./doop 1 / 0 | cat -e
+No division by 0$
+student@ubuntu:~/piscine/test$ ./doop 1 % 0 | cat -e
+No modulo by 0$
+student@ubuntu:~/piscine/test$ ./doop 1 "*" 1
 1
 ```