inversée

A Reverse Polish Notation (Polonaise inversée) calculator for Linux, built to look and feel like a native GNOME application.

inversée \ɛ̃.vɛʁ.se\
French, past participle, feminine singular, of "inverser".

Install

curl -L -o /tmp/inversee.flatpak \
    https://github.com/benjaminbellamy/inversee/releases/download/1.3.2/inversee-1.3.2.flatpak \
    && flatpak install --user --bundle /tmp/inversee.flatpak

Features

• Unbounded stack (Forth/dc-style); every level is visible at once.
• Arbitrary-precision arithmetic via MPFR (128-bit internal precision, ~38 decimal digits).
• Adwaita / GTK 4 interface, follows the system light/dark theme and accent.
• Full RPN operation set: +, −, ×, ÷, mod, %, x^y, √, 1/x, +/−; stack ops swap, drop, rot, dup, dup2, clear.
• Unbounded undo (capped at 1000 entries per session).
• Configurable number format (see below): pick Automatic, the system convention, or a fixed one (1,234.56, 1 234,56, 1.234,56) for display, copy, and paste — applied live, no restart.
• Tolerant clipboard paste: ignores currency symbols, units, and labels around a number, accepts thin / non-breaking thousands separators, smart digit grouping, scientific notation, and both decimal separators.
• Clipboard: copy X, copy the whole stack (one value per line), paste a list of values separated by ;, newlines, or tabs.
• Translations: English (source), French, German, Italian, Spanish, Dutch, Polish, Portuguese — switchable from the in-app menu.
• Fully offline — no network access, no telemetry.

Usage

Inversée uses Reverse Polish Notation (RPN): operands first, then the operator. Devised by Polish logician Jan Łukasiewicz in the 1920s and made famous by Hewlett-Packard pocket calculators, RPN makes parentheses unnecessary — the machine evaluates expressions left to right exactly the way you type them.

To compute 2 + 3: type 2, press Enter, type 3, press +. The stack shows 5. The whole stack stays visible; the newest value, labelled 1:, is the top, and operators consume from the top down. Reorder with swap, drop and rot, undo any change with Ctrl+Z (redo with Ctrl+Shift+Z), and click any stack value to copy it. The in-app About Inversée entry shows the same quick-start, and Keyboard Shortcuts lists every key.

Status

Released. Core engine and UI work end-to-end; the stack and undo history persist across launches.

Keyboard shortcuts

Key	Action
0–9	Digit entry
. or ,	Decimal separator (locale-tolerant)
Enter	Push entry / duplicate X
Backspace	Delete last char / drop X
+ − × ÷	Arithmetic
% / ^	Percent of / power (x^y)
r / i / n	Square root / inverse 1/x / negate
m / s / d / t	mod / swap / drop / rot
Escape	Clear stack
Ctrl+Z	Undo
Ctrl+C / Ctrl+V	Copy X / paste
Ctrl+Shift+C	Copy entire stack
F10	Open the main menu

The same shortcuts are reachable from the on-screen keypad and the hamburger menu's Keyboard Shortcuts dialog.

Using your keyboard's Calculator key

Many keyboards expose a Calculator key that GNOME binds to gnome-calculator by default. To use Inversée instead, open the hamburger menu and pick Reassign calculator key… — the dialog walks you through GNOME Settings → Keyboard, clearing the existing Launch Calculator shortcut and adding a Custom Shortcut that runs Inversée when you press the key.

Number format

The hamburger menu's Number format submenu picks the decimal separator, thousands separator, and clipboard behaviour for display, copy, and paste at once. Stored values are unaffected, and the change applies live.

The default Automatic mode is the one to keep in everyday use. Display and copy follow your system locale, while paste stays tolerant: it accepts either decimal separator, strips currency symbols, units, and labels around a number, handles smart digit grouping, and reads scientific notation. So a value copied from a PDF, a spreadsheet, or a web page that uses another locale just works — no re-typing or clean-up needed.

Choice	Example	Behaviour
Automatic	(default)	Display and copy follow the system locale; paste is best-effort across conventions.
System	shows yours	Display, copy, and paste all follow the system locale strictly.
1,234.56	US / UK	Period decimal, comma grouping.
1 234,56	French	Comma decimal, narrow-space grouping.
1.234,56	German, Spanish, Italian, Dutch, Polish, Portuguese	Comma decimal, period grouping.

Concretely, in Automatic mode:

• Leading or trailing non-numeric characters (currency symbols, units, labels) are ignored: Total: 1,234.56 € → 1234.56.
• Values are separated by ;, newlines, or tabs. A bare space is a thousands separator when it groups three digits (304 650 → 304650) but separates values otherwise (1 2 3 → three values).
• In Automatic mode, when a number contains both . and , the rightmost is the decimal point, so 1,234.56 and 1.234,56 both read correctly. A lone comma is a decimal point only when your locale uses one.

Build

Local (host)

Requires meson, ninja, valac, gettext, plus the development headers for GLib, GTK 4, libadwaita, MPFR, and json-glib.

meson setup build
meson compile -C build
meson test -C build --print-errorlogs
./build/src/inversee

The binary can be run uninstalled directly from the build tree — translations, the GSettings schema, and the application icon are all discovered from the build directory when launched that way.

Flatpak

The Flatpak manifest is the canonical build reference.

flatpak-builder --user --install --force-clean \
    build-flatpak build-aux/fr.benjaminbellamy.Inversee.yaml
flatpak run fr.benjaminbellamy.Inversee

Tests

The numeric and stack engine is a pure-logic static library (libinversee-core) with no GTK dependency. It ships with GLib-based test binaries for every module:

meson test -C build --print-errorlogs

License

GPL-3.0-or-later. See LICENSE.

Author

Benjamin Bellamy <benjamin@castopod.org>