unsure-calc

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.
• A currency suffix on a range applies to the whole range: 1~10eur is the same as (1~10)eur, and 10eur~20eur is a range in EUR.
• 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 }).
• a~b is sampled as a normal distribution with a and b at its P5 and P95. A range that does not cross zero never samples across it, so 1~10 stays non-negative.
• Sampling uses a fixed seed (42), so the same expression always gives the same simulated numbers.
• The likely range defaults to P5-P95. Pick another with the presets or by dragging the band edges on the histogram (arrow keys work on a focused edge); it is kept in the URL as ?p=10-90.
• The web app keeps the last 30 expressions it calculated (typed or opened from a link) in localStorage. Focus the input (or click the clock icon) for a dropdown of them, filtered as you type; Up/Down and Enter rerun one, Shift+Delete or the x removes one. Nothing leaves the browser.
• The web chart draws the samples as a smoothed density curve (Gaussian kernel, Silverman bandwidth). Hover it for the share of outcomes at or below a value; "Show as table" lists the binned counts.

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

Getting started

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.

Project structure (root)

• 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

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Makefile cheatsheet

• 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).