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.

See docs/design-notes.md for the original product vision and non-goals.

Quick start

nix build .
./result/bin/improvise examples/demo.improv

Or import your own CSV:

./result/bin/improvise import path/to/data.csv

The included examples/demo.improv was generated from examples/demo.csv:

improvise import examples/demo.csv \
  --no-wizard \
  --category Region --category Product --category Customer \
  --measure Revenue --measure Cost \
  --time Date --extract Date:Month \
  --axis Region:row --axis Product:row \
  --axis Date_Month:column --axis Measure:column \
  --axis Customer:page --axis Date:none \
  --formula "Profit = Revenue - Cost" \
  --name "Acme Sales Demo" \
  -o examples/demo.improv

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

With Nix (preferred)

nix build .
# or install into your profile:
nix profile install .

From crates.io

cargo install improvise

Prebuilt binaries

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

The data model

Every cell lives at the intersection of named categories and items — (Region=East, Measure=Revenue) — not at a grid address like B3. A model can have up to 12 categories, each with an ordered list of items that can be organized into collapsible groups (e.g. months grouped into quarters).

Formulas reference dimension names, not cell addresses:

Profit = Revenue - Cost
Tax = Revenue * 0.08
Margin = IF(Revenue > 0, Profit / Revenue, 0)
BigDeal = Sum(Revenue WHERE Region = "West")

The formula language supports + - * / ^, comparisons, IF, and aggregation functions (Sum, Avg, Min, Max, Count) with optional WHERE clauses. Formulas apply uniformly across all intersections — no copying, no dragging, no $A$1 anchoring.

Views and axes

A view assigns each category to one of four axes: row, column, page (slicer), or hidden. The grid layout is a pure function of (Model, View) → GridLayout — transposing is just swapping row and column assignments, and it happens in one keystroke (t). Page-axis categories act as filters: [ and ] cycle through items.

Press T to enter tile mode, where each category appears as a tile in the tile bar. Move between tiles with h/l, then press Space to cycle axes or r/c/p to set one directly.

Records mode (R) flips to a long-format view by assigning the virtual _Index and _Dim categories to row and column axes. Drill-down (>) on an aggregated cell captures a snapshot; edits accumulate in a staging area and commit atomically on exit.

File format

Models persist to a plain-text .improv format that reads like markdown and diffs cleanly in git:

# Sales 2025

## Category: Region
- North
- South
- East [Coastal]
- West [Coastal]
> Coastal

## Category: Measure
- Revenue
- Cost
- Profit

## Formulas
- Profit = Revenue - Cost [Measure]

## Data
Region=East, Measure=Revenue = 1200
Region=East, Measure=Cost = 800

## View: Default (active)
Region: row
Measure: column
format: ,.2f

Gzip-compressed .improv.gz is also supported. Legacy JSON is auto-detected for backward compatibility.

Import and scripting

The import wizard analyzes CSV columns and proposes each as a category (string-valued), measure (numeric), time dimension (date-like, with optional year/month/quarter extraction), or skip. Multiple CSVs merge automatically with a synthetic "File" category.

All model mutations go through a typed command registry, so the same operations that back the TUI work headless:

# single commands
improvise cmd 'add-cat Region' 'add-item Region East' -f model.improv

# script file (one command per line, # comments)
improvise script setup.txt -f model.improv

In the browser

The browser page is at https://fiddlerwoaroof.github.io/improvise/, built and published from main by the pages-build / pages-deploy jobs in .github/workflows/ci.yml. A deploy only happens after cargo test and the wasm32 check have passed.

It needs no server. The page is still a thin client — it holds no model, and every question about a cell, its text and whether it may be typed into, is answered by a server and arrives already decided — but the server it talks to is an in-page Web Worker hosting the whole App over the browser's private storage (OPFS). It is seeded on first load from web/demo.improv, so a visitor lands on a document, and edits persist across a reload without leaving the machine. ?doc= and ?seed= name another document and the file it is first seeded from.

To run the same page locally:

./web/build.sh                              # wasm-pack -> web/{pkg,worker-pkg}
python3 -m http.server 8080 --directory web

To open a document hosted by a separate process instead — which is how a document open in the TUI is shared — start the websocket server and pass ?ws=:

cargo run -p improvise-ws-server -- examples/demo.improv --port 8787

then reload with ?ws=127.0.0.1:8787.

The scheme is not yours to supply and defaults to TLS. ?ws= takes a host:port; the page uses wss:// when it is itself served over https and ws:// when it is served over http, because an https origin refuses a ws:// address as mixed content. An explicit ws:// from an https page is upgraded rather than passed through — passing it through can only produce a failure that reads like "the server is not running".

So the local pairing above works as written. Reaching a server from the deployed https page means terminating TLS in front of it (a reverse proxy or a tunnel): improvise-ws-server speaks plain ws:// only, and native wss:// is not implemented.

Caveat worth stating plainly: no line of the browser JavaScript has ever run. There is no browser and no headless DOM in the development environment, so web/app.js, web/worker.js and the OPFS backend are compile-checked, syntax-checked and read, never executed.

What's interesting about the architecture

All user actions flow through a two-phase command/effect pipeline. Commands are pure functions: they receive an immutable CmdContext (model, layout, cursor position, mode) and return a list of effects. Effects are the only things that mutate app state, and each one is a small, debuggable struct. This means commands are testable without a terminal, effects can be logged or replayed, and the 40+ commands and 50+ effect types are all polymorphic — dispatched through trait objects and a registry, not a central match block. The keybinding system gives each of the 14 modes its own keymap, with Emacs-style prefix keys for multi-stroke sequences.

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

Apache-2.0