Polish notation
The definitions above use infix notation for binary connectives such as formula_18. A less common convention is Polish notation, in which one writes formula_22, formula_23 and so on in front of their arguments rather than between them. This convention is advantageous in that it allows all punctuation symbols to be discarded. As such, Polish notation is compact and elegant, but rarely used in practice because it is hard for humans to read. In Polish notation, the formula