improvise/README.md

improvise

Terminal pivot-table modeling in the spirit of Lotus Improv — multidimensional cells, formulas over dimensions instead of cell addresses, and vim-style keybindings for reassigning axes on the fly.

Why this exists

Lotus Improv (NeXT, 1991) separated data from its presentation: cells were addressed by named dimensions, not grid coordinates, and rearranging a view didn't break formulas. That idea never made it into mainstream tools. Excel pivot tables borrowed the visual rearrangement but kept cell-address formulas. Terminal data tools like sc-im and VisiData do different things well — sc-im is a traditional spreadsheet, VisiData is a data explorer — but neither offers the dimension-keyed data model that made Improv interesting. improvise is a small attempt to bring that model to a modern terminal, with a formula language that references category and item names, views that can be rearranged with a single keystroke, and a plain-text file format you can diff in git.

Quick start

nix develop
cargo build --release
./target/release/improvise examples/demo.improv

Or import your own CSV:

./target/release/improvise import path/to/data.csv

Key bindings to try first

Key	Action
T	Enter tile mode — reassign category axes
[ / ]	Cycle through page-axis items
>	Drill into an aggregated cell
<	Return from drill-down
F	Open the formula panel
t	Transpose rows and columns
? / F1	Full key reference
:w	Save
:q	Quit

Installation

From source with Nix (preferred)

nix develop
cargo build --release
# optionally install to your PATH:
cargo install --path .

From crates.io

cargo install improvise

Prebuilt binaries

See the GitHub releases page for prebuilt binaries (Linux x86_64, macOS Intel and Apple Silicon).

What's interesting about the codebase

The data model stores every cell at the intersection of named categories and items — (Region=East, Measure=Revenue) — rather than at a grid address like B3. A view is a configuration that assigns each category to a row, column, page, or hidden axis, and the grid layout is computed as a pure function from (Model, View) to GridLayout. Transposing a pivot is just swapping the row and column assignments; records mode is just assigning the virtual _Index and _Dim categories to particular axes. The formula language references dimension names (Profit = Revenue - Cost), so formulas survive any rearrangement without rewriting. All user actions go through a command/effect pipeline: commands are pure functions that read an immutable context and return a list of effects, which are the only things that mutate state. The same command registry serves both the interactive TUI and the headless cmd/script CLI subcommands. Models persist to a markdown-like .improv format that is human-readable, git-diffable, and optionally gzip-compressed.

Expectations

improvise is a personal project I built for my own use. I'm sharing it because other people might find it useful, but I can't promise active maintenance or feature development. Issues and PRs are welcome but may not get a fast response. If you want to build on it, fork away.

License

MIT