C++ Scientific & Programmer Calculator

A full-stack scientific and fixed-width programmer calculator with an authoritative C++17/Drogon backend, a custom expression parser, REST APIs, Docker packaging and automated verification.

Open the live calculator · API reference · Architecture

The browser handles presentation and interaction. Scientific parsing, input validation, base conversion and programmer operations run in C++; the frontend does not use JavaScript eval().

Recruiter quick view

Area	Evidence
Problem	Deliver scientific and fixed-width programmer calculations through one responsive browser interface.
Engineering depth	Recursive expression parsing, two's-complement interpretation, 8/16/32/64-bit arithmetic, bitwise operations, rotations and defined overflow behavior.
Architecture	Browser UI → JSON REST API → C++17/Drogon scientific and programmer engines.
Verification	GitHub Actions builds the production Docker image and checks health, metadata, calculations, invalid input and frontend delivery.
Operations	Health and metadata endpoints, request IDs, uptime reporting, container deployment and a branded canonical URL.

Capabilities

Scientific mode

• Operator precedence, parentheses, unary operators and implicit multiplication
• Exponentiation, factorial, square root, absolute value and logarithms
• sin, cos and tan in degree or radian mode
• pi and e constants
• Memory, previous-answer recall, history and copy controls

Examples: 2 + 3 * 4, (2 + 3) * 4, sqrt(144), sin(30), log(100) + ln(e).

Programmer mode

• Binary, octal, decimal and hexadecimal input/output
• 8-, 16-, 32- and 64-bit word sizes
• Signed and unsigned two's-complement interpretation
• AND, OR, XOR, NOT, left/right shifts, ROL, ROR and individual bit toggling
• Arithmetic right shift in signed mode
• Wrap-to-selected-width overflow behavior
• Persistent mode, base, width, signedness, current value and history settings

For example, 11111111 is 255 unsigned and -1 signed in 8-bit mode. An 8-bit 128 << 1 wraps to 0 because only the lowest eight bits remain.

Architecture

Browser UI
    |
    | HTTP / JSON
    v
Drogon REST API
    |
    +--> Scientific parser
    |
    +--> Fixed-width programmer engine

The browser owns rendering, keyboard interaction, history presentation and local preferences. The backend owns parsing, calculations, validation, integer interpretation and API responses. See docs/ARCHITECTURE.md for the detailed design.

API

Method	Endpoint	Purpose
GET	/health	Service health, uptime and capability summary
GET	/api/info	Machine-readable application metadata
POST	/api/evaluate	Scientific expression evaluation
POST	/api/programmer	Base conversion and programmer operations

Scientific request:

{
  "expression": "sin(30)",
  "mode": "DEG"
}

Programmer request:

{
  "operation": "AND",
  "left": "12",
  "right": "10",
  "base": "DEC",
  "width": 8,
  "signed": false
}

See docs/API.md for request and response details.

Run locally

docker build -t scientific-calculator-cpp .
docker run --rm -p 8080:8080 scientific-calculator-cpp

Open http://localhost:8080. Health and metadata are available at /health and /api/info.

Verification

The GitHub Actions workflow builds the same multi-stage Docker image used for deployment, starts the service and verifies:

• health, API metadata and frontend delivery;
• scientific arithmetic, DEG/RAD trigonometry and invalid expressions;
• conversions, signed/unsigned ranges and supported word sizes;
• bitwise operations, shifts, rotations and bit toggling; and
• response security behavior.

Security and scope

The application does not require accounts and should not collect personal information. Inputs are untrusted and are validated by the C++ backend. Calculation defects can use the public issue form; exploitable weaknesses should be reported privately according to SECURITY.md.

This is an independently built portfolio project, not a safety-critical, financial or cryptographic calculation service. Verify results independently before using them for consequential decisions.

Repository map

backend/        C++17/Drogon server and calculation engines
frontend/       Accessible browser interface and discovery files
docs/           API and architecture documentation
.github/        CI, dependency updates and issue templates
Dockerfile      Reproducible multi-stage build
CHANGELOG.md    Release history

Roadmap

• OpenAPI specification and structured logging
• Rate limiting and additional resource guards
• IEEE-754 visualization and engineering notation
• Complex numbers, matrices, statistics and graphing
• Automated releases and semantic version tags

Contributing

Focused bug reports, calculation edge cases, accessibility improvements and tests are welcome. Read CONTRIBUTING.md before opening an issue or pull request.

License

Licensed under the MIT License.