calcli

A fast terminal calculator (TUI) with an editable history, stored variables and a few helpers engineers reach for. Built with Ratatui.

Type an expression, press Enter, keep going. The previous result is available as ans, every line stays in an editable history (editing a line recomputes everything below it), and results keep full f64 precision internally even when the display is rounded.

Features

• History with recompute – each entry shows the input with its result on the line below (both soft-wrap long content). Edit any earlier line and every line below is re-evaluated, so ans chains stay correct.
• Full precision – the rounded value you see is only for display; further math always uses the exact internal value.
• Three views – Calc, Variables and Settings, switched with Alt+1 / Alt+2 / Alt+3 (the Calc view is a text field, so bare digits stay typeable). The active view is restored on the next start.
• Variables – save with =name (stores the last answer) or name = expr. Manage them in their own view: insert, copy, delete, reset all. Persisted.
• Notation – cycle decimal / scientific / SI-prefixed (F2); trailing fractional zeros are dropped by default (12, not 12.000), toggle with F6 or the trim_trailing_zeros config key.
• Angle mode – toggle degrees / radians for trig (F3).
• Lenient input – spaces, _ and the non-decimal one of ./, are accepted as thousands separators; SI prefixes like 3.3k, 100u are expanded. Function arguments use ; (e.g. max(1;2)).
• Clipboard – y copies the plain, full-precision value (no grouping); Y copies it as shown (rounded, grouped).
• Growing input – long expressions soft-wrap and the input field grows (up to input_max_lines); ↑/↓ move the caret across the wrapped lines, ↑ on the first line enters the history.
• Syntax highlighting – functions, constants, operators (bold), numbers, defined variables, units, parentheses and ans are coloured in the input, the history and while editing. Colours are configurable in the [highlight] table; unknown identifiers stay neutral.
• Live feedback – as you type, the input border shows a dim = value preview while the expression is valid and a subtle warning marker when it looks complete but won't parse (silent while still mid-typing). Toggle with live_feedback in the config.
• Settings view – every display setting on one editable list (←/→ steps the focused value, applied live), including the theme and the glyph set. The function keys keep working from every view.
• Shortcut hints – the footer lists the current view's keys, grouped, with a closing Global group. F1 hides the whole band (the state is remembered); F12 or ? opens the scrollable, fuzzy-filtered help overlay.
• Persistence – settings, variables, history and the interface state (active view, theme, glyphs, hint visibility) are saved on exit and restored next time (settings restore is configurable). Writes are atomic, and a state.toml from any older calcli still loads.

Install

calcli builds on Rust 1.88 or newer (MSRV).

From crates.io:

cargo install calcli

Or from a local checkout:

cargo install --path .

Or run without installing:

cargo run --release

Start with --demo to fill the session with sample data (history, variables, unit conversions) for a quick tour – demo mode never writes to your saved session:

calcli --demo

Keys

Every key below is rebindable under [keys] in the config. The footer and the help overlay (F12 or ?) are both generated from the same action catalog, so they can never disagree with each other. Ctrl+Q and F1 belong to the toolkit and cannot be rebound.

Global

Available everywhere. The function keys and Alt chords also work while typing, because they can never be part of an expression.

Alt+N reaches the app only if your terminal sends Alt as a meta prefix. Ghostty, WezTerm, Alacritty and kitty do by default. In iTerm2 set Left Option key to Esc+; in macOS Terminal.app enable Use Option as Meta key. Otherwise rebind view_calc / view_variables / view_settings under [keys] – F4 already reaches the Variables view unaided.

q and ? are ordinary characters while the input or an in-place edit has the keyboard, so they are typed rather than acted on. Use :q to quit from there.

With confirm_quit = true the soft quit (q, :q) asks first; Ctrl+Q never asks. Both save the session on the way out.

Calc – typing

Typing an identifier opens a suggestion dropdown of matching variables, built-in functions and constants. ↑ / ↓ pick a suggestion, Enter / Tab / → accept it, and Esc closes the dropdown. While it is open ↑ steers it rather than the history, so use PgUp to browse the history from there.

Calc – browsing the history (after ↑)

Reordering, inserting and deleting all re-evaluate the affected lines, so ans and variable assignments stay consistent with the new order.

Calc – editing a line in place

Switching views is locked while a line is being edited; the tab bar dims to say so. Finish or cancel the edit first.

Variables (Alt+2 or F4)

Settings (Alt+3)

Notation, decimals, angle mode, trailing zeros, the decimal and thousands marks, the glyph set and the theme. The theme and glyph choice are persisted.

Typed commands (in the input)

:d[n], :s[n], :si[n] set notation (and optional decimals); :deg / :rad set the angle mode; :clear clears the history (asks first); :q quits.

Expressions

Backed by meval: + - * / ^ (and ** for power), parentheses, constants pi, e, and functions such as sqrt, exp, ln, abs, sin, cos, tan, asin, acos, atan, sinh/cosh/tanh, floor, ceil, round, min, max, atan2. Trig respects the angle mode.

• ans – the previous result. A line starting with an operator (e.g. +5) continues from it automatically.
• =name – save the previous answer to name.
• name = expr – evaluate and store. ans, pi and e are reserved.
• SI prefixes on numbers: k M G T m µ u n p (e.g. 4.7k → 4700).
• Units, conversion & arithmetic: write a quantity as value unit (space-separated, e.g. 123 MPa) and convert with -> (or to): 123 MPa -> bar, 1 l -> dm^3, 100 km/h -> m/s, ans -> psi, x = 50 kN then x -> N. You can also calculate with units – 20 kN + 300 N → 20.3 kN, 1 m + 50 cm → 1.5 m, 1 m * 2 m → 2 m^2, 2 kN / 4 m^2 -> kN/m^2 → 0.5 kN/m^2. ans and variables keep their unit. Units are powered by rink-core; a conversion is shown in the unit you typed, a derived result in a sensible symbol (pin any other unit with ->). Exponents use ^ (cm^3, m^2).
• Comments: everything after # is ignored by the calculation but kept in the history (e.g. 2*pi*r # circumference). A line that is only a comment is kept as a note (no result); notes don't break the ans chain.

Configuration

calcli reads config.toml from $XDG_CONFIG_HOME/calcli/ (or ~/.config/calcli/). Every key is optional, and merging is per key rather than per section. See examples/config.toml for the full, commented list.

Environment variables override the file for a single run: CALCLI_DECIMALS, CALCLI_DECIMAL_SEPARATOR, CALCLI_THEME, CALCLI_ACCENT, CALCLI_GLYPHS, CALCLI_CONFIRM_QUIT, CALCLI_CONFIRM_DELETE.

A config.toml written for calcli 0.2 (a flat [theme] table and a top-level glyphs key) still loads unchanged; its colours are mapped onto the sections above. The 0.2 shape is deprecated but supported.

The session (settings, variables, history and the interface state) is stored in state.toml under $XDG_STATE_HOME/calcli/ (or ~/.local/state/calcli/); see examples/state.toml. It is written atomically, and a state.toml from any earlier calcli still loads. History values are recomputed on load so the ans chain stays consistent with the active settings.

glyphs = "ascii" switches the warning marker and the toolkit's list markers to ASCII; borders and a few separators use broadly-compatible Unicode box-drawing and middle-dot glyphs.

Architecture

Layered, with the composition root in main.rs and dependencies pointing inward to domain:

• domain/ – pure core: evaluation (Evaluator trait + meval), the units engine (rink), expression preprocessing, number formatting, variables, history (and its replay), and the domain error type.
• services/ – CalcService: orchestration (submit / edit / delete + recompute, variables, settings). Also the error funnel: a StorageError is converted here into a domain error, so nothing below names files or TOML.
• storage/ – StateRepository port + an atomic TOML implementation.
• config/ – Config, the appearance/highlight sections and the loader (defaults → TOML → CALCLI_*).
• keymap.rs – the action catalog: the single source for key dispatch, the footer hints, the help overlay and the [keys] config names.
• tui/ – the Ratatui front-end: a shared appframe, one module per view, and an Interaction port so the key path is testable without a terminal.
• util/ – atomic writes, paths, logging.

The terminal toolkit (widgets, theming, modals, the event loop, the clipboard) comes from ratada, so calcli holds no copy of it. The one deliberate exception is tui/text_edit.rs: calcli syntax-highlights its input per character, and ratada's text widgets render plain text only.

Dimensionless math runs through the Evaluator trait (meval), keeping full f64 precision and the angle mode; anything involving units is routed to the domain::units wrapper around rink-core, which owns conversion and unit arithmetic.

Development

cargo fmt --check                        # formatting
cargo clippy --all-targets -- -D warnings  # must be warning-free
cargo test                               # unit + integration tests
cargo run -- --demo                      # a session filled with sample data

See docs/DEVELOPMENT.md for the project layout and CLAUDE.md for the coding standards this project follows.

When you change a shortcut, the footer and the help overlay follow the action catalog in src/keymap.rs automatically – but the key tables in this README and the [keys] block in examples/config.toml have to be updated by hand.

License

Licensed under the MIT License.