rpncalc exam exercise readme

subjects/rpncalc.en.md

@@ -0,0 +1,60 @@
+## rpncalc
+
+### Instructions
+
+Write a program that takes a string which contains an equation written in
+Reverse Polish notation (RPN) as its first argument, evaluates the equation, and
+prints the result on the standard output followed by a newline.
+
+Reverse Polish Notation is a mathematical notation in which every operator
+follows all of its operands. In RPN, every operator encountered evaluates the
+previous 2 operands, and the result of this operation then becomes the first of
+the two operands for the subsequent operator. Operands and operators must be
+spaced by at least one space.
+
+The following operators must be implemented : `+`, `-`, `*`, `/`, and `%`.
+
+If the string is not valid or if there is not exactly one argument, `Error` must be printed
+on the standard output followed by a newline.
+If the string has extra spaces it is still valid.
+
+All the given operands must fit in a `int`.
+
+Examples of formulas converted in RPN:
+
+3 + 4                   >>    3 4 +
+((1 * 2) * 3) - 4       >>    1 2 * 3 * 4 -  ou  3 1 2 * * 4 -
+50 * (5 - (10 / 9))     >>    5 10 9 / - 50 *
+
+Here is how to evaluate a formula in RPN:
+
+```
+1 2 * 3 * 4 -
+2 3 * 4 -
+6 4 -
+2
+```
+Or:
+
+```
+3 1 2 * * 4 -
+3 2 * 4 -
+6 4 -
+2
+```
+And its output :
+
+```console
+student@ubuntu:~/student/rpncalc$ go build
+student@ubuntu:~/student/rpncalc$ ./rpncalc "1 2 * 3 * 4 +" | cat -e
+10$
+student@ubuntu:~/student/rpncalc$ ./rpncalc 1 2 3 4 +" | cat -e
+Error$
+student@ubuntu:~/student/rpncalc$ ./rpncalc | cat -e
+Error$
+student@ubuntu:~/student/rpncalc$ ./rpncalc "     1      3 * 2 -" | cat -e
+1
+student@ubuntu:~/student/rpncalc$ ./rpncalc "     1      3 * ksd 2 -" | cat -e
+Error$
+student@ubuntu:~/student/rpncalc$
+```