a command-line RPN calculator implemented in Rust
*to be backronym'd!
Post-fix notation, also called Reverse Polish Notation (RPN) after its creator Jan Łukasiewicz, is a mathematical notation in which operators (such as + or %) follow their operands. For example, the infix expression 3 + 4 can be written in RPN as 3 4 +. For operators with fixed arity (fixed number of operands) this notation uniquely describes the expression without the need for parentheses to distinguish the order of operations.
[postfix] A B C D * + / == (A (B (C D *) +) /) == [infix] A / (B + (C * D))
[postfix] A B * C + D / == (((A B *) C +) D /) == [infix] ((A * B) + C) / D
rpn uses binary operators, i.e. all operations act on two operands.
See wikipedia/Reverse_Polish_notation for more info.
Requires an installation of Rust. Recommended build profile is release:
$ curl https://sh.rustup.rs -sSf | sh # install Rust
$ git clone https://github.com/drvog/rpn # clone repository
$ cd rpn # change into source directory
$ cargo run --release # compile and run
rpn should run on UNIX-like (Linux, MacOS, BSD, etc.) terminal emulators and Windows 10+ (CMD.EXE or Powershell).
rpn can be started in the root of the cargo directory structure:
$ cd rpn
$ cargo run --release
____________ _ _
| ___ \ ___ \ \ | |
| |_/ / |_/ / \| |
| /| __/| . ` |
| |\ \| | | |\ |
\_| \_\_| \_| \_/
Version 0.1.0
___________________
rpn> 3 4 +
===> 3 4 +
= 7
From here you can input calculations (in postfix notation, of course) which will be evaluated. If you input a valid expression it will output after the =. To exit the interpreter you can enter quit or exit. The expression help will print out some useful explanation. Thanks to the handy rustyline crate, previous input history can be accessed with the UP/DOWN keys.
- Variable declaration?