ポーランド記法
In reverse Polish notation, the operators follow their operands; for instance, to add 3 and 4 together, one would write rather than . If there are multiple operations, operators are given immediately after their second operands; so the expression written in conventional notation would be written in reverse Polish notation: 4 is first subtracted from 3, then 5 is added to it. An advantage of reverse Polish notation is that it removes the need for parentheses that are required by infix notation. While can also be written , that means something quite different from . In reverse Polish notation, the former could be written , which unambiguously means which reduces to (which can further be reduced to -17); the latter could be written (or , if keeping similar formatting), which unambiguously means .