Boost.OpenMethod

Open-methods are free-standing functions that work like virtual functions: they select the best overrider from a set, depending on the dynamic type of their arguments. This makes it possible to add polymorphic operations to existing classes, without modifying them. They make patterns like Visitor unnecessary.

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About Boost.OpenMethod

Please check out the library's documentation to learn more.

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Quick Start

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Boost.OpenMethod

This page gives a 10,000-foot view of the library. For the motivation, tutorials and reference, please follow the documentation link.

Features

Free-standing virtual functions, similar to CLOS, Clojure, Julia, Dylan, etc.
Single dispatch can be as fast as equivalent virtual function calls.
Multiple dispatch in constant time (for a given number of virtual parameters).
Redundancy-free multiple dispatch tables.
Inter-operation with standard smart pointers, extensible to other pointer-like types.
Exception agnostic by default.
Macro-based interface for convenience.
Macro-free interface for inter-operation with templates.
Customization points for alternative RTTI systems, error handling, vptr placement, etc.
Header-only.

Requirements

The library requires an optimizing compiler supporting C++17 or above.

Tested Compilers

Boost.OpenMethod is tested with the following compilers:

clang: 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20
gcc: 8, 9, 10, 11, 12, 13, 14, 15
msvc: 14.3
icpx

…on the following platforms:

Linux
macOS
Windows
s390x

Quality Assurance

The development infrastructure for the library includes these per-commit analyses:

Coverage reports
Clang sanitizers
Compilation and tests on Drone.io and GitHub Actions

Build Status

Branch GH Actions Coverity Scan codecov.io Deps Docs

master

develop

Community

Questions, suggestions, defect reports, etc can be submitted via the following channels:

Slack. Best for quick questions, especially for those getting started with the library.
The Boost developers mailing list. Best for in-depth discussion of the features, future, and implementation of the library. Be sure to read the discussion policy before posting. Please add the [openmethod] tag at the beginning of the subject line.
Issues page on GitHub. Best for bug reports. Please mention the Boost version, platform and compiler you are using, and provide a small compilable code sample to reproduce the problem. Also a good place for feature requests and suggestions.