Reverse Polish Notation basic calculator with some functions.

• Reverse polish calculator is a basic calculator that receives it's operand after it's operators.
• It's input will be like: (operand) (operand) (operator).
• For instance, if we want to calculate the formula "3 + 4" we would write it in the form: "3 4 +" to the input of the calculator.
• Also, "(1 - 2) * (4 + 5)" is entered as 1 2 - 4 5 + *.
• This calculator needs no parenthesis. When it receives an operator, it perform the operation on the last two operands behind it.
• This calculator supports double-precision for all operands
• This project is intended to make a small reverse polish calculator.
• Please input operators and operands each separated by a space or a tab.

• Trigonometric functions embedded in this program is: sin, cos, tan, exp, pow and sqrt.

Example
90 sin↵

Result
1

Example
2 exp↵

Result
7.3890561

Example
5 2 pow↵

Result
23

print order will print the top value of the stack.

Example
print↵

Result
8.34

dup order will duplicate it's operand.

Example
5 dup *↵

Result
25

swap order will swap the previous two operators.

Example
2 5 swap /↵

Result
2.5

clear order will clear the contents of stack[] and store[].

Example
clear↵

Result

stack cleared!   
store cleared!

store order will store the previous value in the corresponding one-char variable.

Example
5.67 store a↵

Result
a = 5.67

view order will view the contents of the corresponding variable/s.

Example
view a↵

Result
a = 5.67

Example
view a-z↵

Result

a = 5.67
b = 0
c = 0
...
z = 0

exit order will exit the program.

Example
exit