Reverse Polish notation (RPN)
Notación polaca inversa (RPN)
- Date
- c. 1957 · confidence medium
- Place
- Sydney, New South Wales, Australia
- Credited to
- Charles L. Hamblin
- Field
- Knowledge & symbols
⚠️ Disputed: the sources disagree.
What it is
Hamblin inverted Jan Łukasiewicz's prefix notation so operators come after their operands, letting an expression be evaluated with a simple stack and no parentheses; the idea was independently rediscovered by Robert S. Barton in 1958 and by Bauer and Dijkstra in the early 1960s to save memory on early computers.
There is no single origin: Hamblin worked out the idea in the mid-1950s in Australia, Robert S. Barton independently reinvented it in 1958 in the US (later used in the Burroughs B5000), and Bauer and Dijkstra independently rediscovered it in the early 1960s in Europe. Wikidata dates the item to 1924, which actually corresponds to Łukasiewicz's original prefix Polish notation, not its reverse form.
What it led to
- Stack-based calculators and programming languages
- Compilers that evaluate expressions without parentheses
Built on
- Łukasiewicz's three-valued logic1920
- Jan Łukasiewicz's Polish notation