LocalizePad

A notepad calculator — type a problem the way you'd write it on paper, get the answer in the margin — built on the Localize stack and deployed as a Phoenix/LiveView app.

Live at pad.elixir-localize.com. No account, nothing stored on the server: a sheet lives in your browser, and sharing one puts it in the URL fragment rather than in a database.

The concept is Soulver's. What makes this one different is two things Soulver structurally cannot do:

• It reads your language, it doesn't merely format in it. 1.234,5 Meter in Kilometer, 20 % von 700, 10 juin + 3 semaines. Switching locale re-parses and re-formats the whole sheet, across 500+ CLDR locales and 18 calendars.

• It knows which English. The locale is a language tag, so 3/4/2026 is 3 April to an en-AU reader and March 4 to an en-US one, and 42.195 km in local units answers in kilometres or miles accordingly. en-GB gets miles and keeps Celsius, because that is what Britain actually does — the answer is CLDR's, not a metric/imperial flag.

• It answers the temporal questions people actually get stuck on. Not just "what date is three weeks from Tuesday", but "when are London, New York and Tokyo all at work" (they never are), "every Friday the 13th from 2027", "when am I free on Tuesday given this .ics", "is Friday a workday" (yes in the US, no in Saudi Arabia).

See plans/localize_pad.md for the full design and delivery plan.

The stack

Library	Role
localize	CLDR formatting, locale-aware number parsing, MF2 messages
calendrical	Locale-aware date/time/interval parsing across 18 calendars
ex_tempo	The temporal value type — intervals, set algebra, recurrence, scheduling
unity	The unit engine — ~2,760 units and unit arithmetic
ex_money	Currencies, exchange rates, financial functions
localize_web	Locale discovery plugs, localized routes, HTML helpers
unicode_string	UAX #29 word segmentation, with ICU dictionaries for scripts written without spaces

Getting started

mix setup

That fetches dependencies, downloads CLDR locale data for the configured :supported_locales and the Unicode word-break dictionaries, creates the database, and builds assets.

The locale data and the dictionaries are downloaded rather than vendored, and the dictionaries matter more than they look: without them a Japanese or Thai line is never segmented, and that degrades silently rather than failing — the line simply stops producing an answer.

Then:

mix phx.server

The app runs at localhost:4000.

Development

mix test

mix precommit

mix precommit compiles with warnings as errors, checks for unused deps, formats, and runs the suite — the same ground CI covers.

Pre-commit hook

The repository ships a mix format pre-commit hook. It is wired automatically for this working copy; on a fresh clone, enable it with:

git config core.hooksPath .githooks

Requirements

Elixir 1.17+ on OTP 27 or later — Tempo does not support OTP 26. The canonical development toolchain is Elixir 1.20 on OTP 29, which is also CI's lint row.

Configuration

Locale behaviour is configured in config/config.exs under :localize. The application-wide default locale can be overridden at deploy time with the LOCALIZE_DEFAULT_LOCALE environment variable.

:supported_locales is a list of language tags, not languages, and the distinction is the product: en-AU and en-US read 3/4/2026 as two different days, so "English" is not an answer to which English. A territory only changes an answer if its data was fetched, and a tag whose data is missing falls back silently — CLDR resolves en-AU to en and hands back US conventions with nothing on screen to say so. So the picker offers exactly the tags in that list, and typing any other tag resolves through CLDR's own inheritance, which is usually right: en-IE inherits en-GB rather than en.

Locale data is downloaded rather than vendored, and the release does not carry it — a production node fetches its own set at boot, so adding a locale is a config change and a restart rather than a rebuild. A locale that cannot be fetched is logged and dropped from the picker instead of being served with another language's rules.

Sales tax has no configured rate and no default. A sheet declares its own with a line like VAT = 15%, and until it does, tax phrases refuse rather than answering. Rates differ by country and by US state, so any value the app picked would be wrong for most people — and wrong quietly, since $0.00 reads like a total rather than like a missing setting. It also keeps a shared pad meaning the same thing to whoever opens it.

Currency conversion needs an Open Exchange Rates app id, set via OPEN_EXCHANGE_RATES_APP_ID. Without it the app runs normally; currency conversion is simply unavailable.

mix setup creates a database because the scaffolding is there for accounts, but nothing in the app reads or writes it yet — a sheet lives in the browser. A production deployment without DATABASE_URL starts without a repository rather than refusing to boot, and that reverts when accounts arrive.

License

Not yet chosen. The libraries this app is built on are Apache-2.0, but LocalizePad is an application rather than a library and its licensing is a separate decision.