A simple example of a calculation in a database

The suffix expression is when the symbol is encountered, the top element of the stack is computed, and the result is pressed back into the top of the stack.
9 2 3 +-10 2/-The calculation process is as follows:
9 2 3 into the stack
Encounter + number, take out 2 3 Add, and the result into the stack, the result is
9 5
The same time, the stack is:
4
Re-entry 10 2, Stack for:
4 10 2
Encountered/number, stack changed to:
4 5
Again, the stack changed to:
-1
Suffix expression ends, so the end result is-1
The suffix expression reverts to infix expression: 9-(2 + 3)-10/2

A simple example of a calculation in a database