A RPN calculator program computes expressions written in RPN (Reverse Polish Notation). A RPN expression (or a postfix expression) is one of the following:
a number X, in which case the value of the expression is that of X;
a sequence of the form E1 E2 O, where E1 and E2 are postfix expressions and O is an arithmetic operation; in this case, the value of the expression is that of E1 O E2
The following are RPN expressions:
20 5 / => (20/5) = 4
4 2 + 3 - => (4+2)-3 = 3
3 5 8 * 7 + * => 3((58)+7) = 141
7 2 - 3 4 = 5 3 4
Suggested scenarios
Given a RPN Calculator when a digit is sent it should display the same digit
Given a RPN Calculator when some digits are sent it should display the number formed by those digits
Given a RPN Calculator when an operation (* + / -) is sent after two numbers it should display the result of that operation
Try it:
lein test
Source: https://gist.github.com/dlresende/274194dd6ec993eb5ec5