RPN - A simple and useful CLI RPN calculator.

Description

rpn is a simple but useful, CLI RPN calculator for Linux. rpn is written in Go and is statically compiled, requiring no external libraries. Installation is as simple as running one command and should work on any Linux distribution.

This is a work in progress, but rpn already supports a rich set of operations and should be useful for daily work.

Motivation

I've been using RPN calculators for a long time and the lack of a simple and convenient CLI version (think bc, but using RPN) frustrated me. I've used dc many times, but it has some quirks that quickly stand in the way of productivity, like having to print the results of the stack every single time, no editing in the command-line, etc.

Looking around the Debian repos and Github revealed some possible alternatives, but they also come with their own set of inconveniences, like:

• Requiring a GUI.
• Requiring the installation of many dependencies (npm, Java runtime, etc).
• Not allowing editing of the command-line, or recall of a previous line.
• Using a TUI (and making editing more complicated).
• Buggy or incomplete implementations.
• Too complex.

The idea of rpn is to be simple and functional enough to be your daily driver RPN calculator. :)

Installation

Automatic process

To download and install automatically (under /usr/local/bin), just run:

curl -s \
  'https://raw.githubusercontent.com/marcopaganini/rpn/master/install.sh' |
  sudo sh -s -- marcopaganini/rpn

This assumes you have root equivalence using sudo and will possibly require you to enter your password.

To download and install under another directory (for example, $HOME/.local/bin), run:

curl -s \
  'https://raw.githubusercontent.com/marcopaganini/rpn/master/install.sh' |
  sh -s -- marcopaganini/rpn "$HOME/.local/bin"

Note that sudo is not required on the second command as the installation directory is under your home. Whatever location you choose, make sure your PATH environment variable contains that location.

Homebrew

RPN is available on homebrew. To install, use:

brew tap marcopaganini/homebrew-tap
brew install rpn

Manual process

Just navigate to the releases page and download the desired version. Unpack the tar file into /usr/local/bin and run a chmod 755 /usr/local/bin/rpn. If typing rpn doesn't work after that, make sure /usr/local/bin is in your PATH. In some distros you may need to create /usr/local/bin first.

Using go

If you have go installed, just run:

go install github.com/marcopaganini/rpn@latest

Limitations and Caveats

This projects uses the excellent decimal math library, by Eric Lagergren, so it inherits its strengths and limitations:

• RPN uses General Decimal Arithmetic.
• Internally, we use the IEEE 754R Decimal128 format, with a precision a maximum scale of 10^128.
• Maximum precision is 34 digits.
• When operating on non-decimal numbers, input is truncated to a uint64 (maximum = 2^64).
• We currently trim trailing fractional zeroes. This means that, for example, 1.23 + 1.27 will give 2.5 as a result, and not 2.50. There are valid applications that require the full precision and we may add an option for that if enough people need it.
• n / 0 == Infinity
• 0 / 0 == Nan
• Anything above 10^128 == +Infinity

Similar projects

There are many other calculators for Linux, and some of them supporting RPN. This is a list of a few that support RPN:

• dc: The venerable dc calculator. One of the oldest Unix programs. Readily available in most distributions. dc is somewhat quirky and does not support many operations, but uses arbitrary precision math and supports truly gigantic numbers.
• dcim: An improved version of dc.
• orpie: A Curses-based RPN calculator (TUI).
• qalculate: A very complete calculator with CLI, GTK, and QT versions. Focus is mostly on the UI part. The author doesn't seem to use RPN so the RPN mode is a bit rough around the edges.

Contributions

Feel free to open issues, send ideas and PRs.