**Polish notation**, also known as **prefix notation** was created by Jan Łukasiewicz. Operators are placed before operands. + 1 2 Yields (as expected) 3. It is not limited to only two values, nor to just addition. (* (+ 0 1) (+ 2 3)) Returns 5. While the examples above use parantheses, one of the benefits of Polish notation is that, assuming the arity of each operator is known, parentheses are unnecessary: the order of operations is unique and easy to determine, if the expression is known to be correct. For example, assuming `*` and `+` are binary, * + 0 1 + 2 3 can refer *only* to (* (+ 0 1) (+ 2 3)) Polish notation is used in computer programming languages Lisp, Scheme (based on Lisp), and some others.
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