C++ Patterns - Patterns
C++ Patterns is a repository of code patterns illustrating a modern and idiomatic approach to writing C++. The aim is to provide beginner to intermediate C++ developers a reference for solving common problems in C++. As the C++ language and library evolve, which they have been doing rapidly since the release of C++11, these patterns will be updated to match the current state-of-the-art in idiomatic C++ development.
This repository contains the source for the patterns themselves, which is used when building the C++ Patterns web front-end. For the front-end source, see sftrabbit/CppPatterns-Web.
To contribute new patterns or edit existing ones, please fork this repository and submit pull requests for your changes. Please read the following guidelines before contributing.
For sample ideas, please see the issues page for suggestions. If you don't feel like writing patterns yourself, feel free to add suggestions to this page.
What makes a good pattern?
A good pattern:
- uses only modern C++ language and standard library features.
- is generic and therefore widely applicable.
- is understandable for C++ beginners.
- acts as a starting point for learning about C++ features.
Each pattern is a
.cpp file that exists within a category and a
section. In the repository, these files have the following path:
The categories are very broad and it is not expected that new
categories will be added any time soon. If your pattern does not
fit into an existing section, feel free to create a new section.
Every category and section contains a
TITLE file, giving the
name of that category or section.
When the web front-end is built, numeric prefixes are stripped from category names and the section is removed. For example, the following pattern source:
is given the following page in the web front-end:
The purpose of removing the section directory is to ensure URLs do not change when moving patterns between sections. For this reason, all pattern file names within a category must be unique.
Even if the title of a pattern changes, please avoid changing the file name. If the pattern changes significantly enough for the file name to change, then it should be a new pattern.
.cpp file must be structured as follows:
// Title // Tag1, Tag2 Example code // Intent paragraph // // Description paragraph #1 // // Description paragraph #2 Hidden code
The title comment and tags comment must each be a single line. The tags comment is optional. The tags line should be a comma separated list of tags.
The intent and description are processed as an extended form of Markdown, which means that they support formatting such as italics, bold text, links, lists, and line references.
The example code section is displayed on the pattern page and should contain everything required to understand the pattern. The hidden code section should contain any additional code that is required in order for the file to compile and is not shown on the pattern page.
Please keep to a width of approximately 70 characters for those who might view the source without wrapping.
The pattern description is processed as a form of Markdown with the following extensions:
Line references are added with the
-YYis optional and used to denote a range of lines. An exclamation mark after the opening bracket causes the output to be capitalized.
The numbers provided should denote line numbers in the original
.cppfile. They will be offset automatically when building the web front-end.
may expand to
[10-14]may expand to
lines 8-12, and
[!15]may expand to
Line 13(note the capital L).
To simplify links to cppreference.com, any link whose URL begins with
cpp/will automatically link to the appropriate page on cppreference.com.
The only strict requirement on code style is that it should be idiomatic and modern C++. The exact formatting of code is not too important - in fact, variations in style can be useful.
There are a few simple guidelines:
autofor two reasons: firstly, the patterns are intended to be used as a reference for beginner C++ developers, and the types involved are important to help with their understanding; secondly, a consensus has not been reached on when it is appropriate to use
Use the uniform initialisation syntax where possible.
Name entities with generic names (
Keep the example code as simple as possible. Give the bare minimum required to understand the pattern.
Do not use inline comments for explaining the pattern - that's what the pattern description should do. Use inline comments only as a placeholder for omitted code.
The writing style for the intent and description are also not strict. However, there are a few guidelines that should be kept in mind:
Use the personal pronoun "we" when describing the pattern, as though you and the reader wrote this code together. It helps to make the description more personable.
Use line references whenever appropriate. It allows the reader cross-reference between the code and the description.
The intent should be a simple sentence or two describing what the purpose of the pattern is.