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

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 (override port with DEV_PORT=9000 make dev).
3. Run make test to execute the Node unit tests.

• index.html — UI shell that loads Tailwind and the calculator script.
• main.js — all calculator logic (tokenizer, shunting yard with unary minus, evaluator, histogram) shared by browser and tests.
• tests/main.test.js — minimal node:test suite covering tokenization, unary minus handling, precedence, and range evaluation.
• 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 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 tests).