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Lightweight probabilistic calculator that lets you type ranges (with ~) and arithmetic to see exact bounds plus simulated outcomes and a text histogram.

It also supports currency expressions with step-by-step simplification, e.g.:

120usd + 50eur to pln

Notes:

• to <currency> converts the expression result to the target currency.
• Trailing arithmetic after conversion is supported (to pln * 20 * 12).
• Web app fetches daily FX rates (once per local day) from Frankfurter/ECB for 25 major currencies (EUR base + 24 symbols).
• Supported symbols in daily feed: EUR, USD, GBP, JPY, CHF, CAD, AUD, NZD, SEK, NOK, DKK, PLN, CZK, HUF, RON, TRY, CNY, HKD, SGD, KRW, INR, MXN, BRL, ZAR, AED.
• If live fetch fails, the app falls back to a local EUR/PLN snapshot (4.22).
• Rates can still be overridden programmatically with evaluateExpressionWithSteps(..., { currencyRates }).

Deployed at: https://calc.pythonic.ninja

1. Install prerequisites: node (v18+ for node:test) and python3 for the simple dev server.
2. Run make dev then open http://localhost:8000/web/ (override port with DEV_PORT=9000 make dev).
3. Run make test to execute the Node unit tests.

• core/calc-core.js — single source of calculator logic used by web, Raycast, and tests.
• core/tests/ — node:test suite covering tokenizer, unary minus, precedence, and range evaluation.
• web/ — static site (Tailwind UI + browser controller).
• raycast-extension/ — Raycast command code and manifest.
• Makefile — quick commands for local dev and tests.

flowchart TD
 A[User Input] --> B[tokenize]
 B --> C[shuntingYard to RPN]
 C --> D[evalRpn UncertainValue]
 D --> E[formatNumber getQuantiles generateTextHistogram]
 E --> F[DOM render web/main.js browser handlers]
 subgraph Tests
 B
 C
 D
 end

• make dev — serve the app via python3 -m http.server $(DEV_PORT) (defaults to 8000).
• make test — run the Node test suite (node --test core/tests/*.test.js).