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@@ -6,152 +6,123 @@ Exceptions. See /LICENSE for license information.
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SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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-->
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-<!-- toc -->
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+## **The Carbon Language project is an experiment exploring a future direction for the C++ programming language.**
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-## Table of contents
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+<p align="center">
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+ <a href="#carbon-goals">Carbon goals</a> |
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+ <a href="#carbon-and-c">Carbon and C++</a> |
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+ <a href="#take-a-look">Take a look</a> |
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+ <a href="#join-us">Join us</a>
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+</p>
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-- [Overview](#overview)
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-- [What about other languages?](#what-about-other-languages)
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-- [Project status](#project-status)
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-- [What will make Carbon a compelling future path for C++?](#what-will-make-carbon-a-compelling-future-path-for-c)
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-- [Contributing](#contributing)
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+<a href="docs/images/snippets.md#quicksort">
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+<img src="docs/images/quicksort_snippet.svg" align="right" width="575"
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+ alt="Quicksort code in Carbon. Follow the link to read more.">
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+</a>
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-<!-- tocstop -->
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+<!-- Don't let the text wrap too narrowly to the left of the above image. -->
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+<div><img src="docs/images/bumper.png">
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-## Overview
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+**Fast and works with C++**</div>
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-The Carbon Language project is an **_experiment_** to explore a possible,
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-distant future for the C++ programming language. It is designed around a
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-specific set of goals, priorities, and use cases:
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+- Performance matching C++ using LLVM, with low-level access to bits and
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+ addresses
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+- Interoperate with your existing C++ code, from inheritance to templates
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+- Fast and scalable builds that work with your existing C++ build systems
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+
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+**Modern and evolving**
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+
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+- Solid language foundations that are easy to learn, especially if you have
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+ used C++
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+- Easy, tool-based upgrades between Carbon versions
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+- Safer fundamentals, and an incremental path towards a memory-safe subset
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+
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+**Welcoming open-source community**
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+
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+- Clear goals and priorities with robust governance
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+- Community that works to be welcoming, inclusive, and friendly
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+- Batteries-included approach: compiler, libraries, docs, tools, package
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+ manager, and more
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+
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+## Carbon goals
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+
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+We believe Carbon must support:
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1. Performance-critical software
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2. Software and language evolution
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3. Code that is easy to read, understand, and write
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-4. Practical safety guarantees and testing mechanisms
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+4. Practical safety and testing mechanisms
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5. Fast and scalable development
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6. Modern OS platforms, hardware architectures, and environments
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7. Interoperability with and migration from existing C++ code
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-The first six of these represent a set of priorities for C++ shared by a
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-significant subset of the C++ community, industry, and ecosystem. However, C++
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-is increasingly constrained by a diverse set of concerns and priorities
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-(including some that are irrelevant to or in opposition to these goals, such as
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-ABI stability), and carries a significant historical legacy that makes it
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-challenging to evolve effectively. The result is that these users struggle to
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-meet our goals using C++ today, and that is unlikely to change in the near
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-future. Carbon is an attempt to explore what it would look like to rapidly and
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-systematically re-engineer C++ into a near optimal future state along the top
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-six priorities, which nonetheless is still reachable through interoperability,
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-tooling, automation, and incremental large-scale migration efforts.
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-
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-For more information, see [our goals document](docs/project/goals.md).
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-
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-## What about other languages?
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-
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-Other programming languages don't _currently_ address these needs effectively.
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-They present interoperability, migration, and performance challenges that make
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-it expensive and potentially impossible to migrate a large C++ code base. An
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-approach which requires rewriting an entire binary at once would be infeasible.
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-A large-scale migration must be incremental, meaning that interoperability and
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-tool-assisted code rewrites are critical.
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-
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-There are projects for several languages to reduce obstacles affecting migration
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-from C++. Some contributors to Carbon are also contributing to those efforts in
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-parallel in order to understand all of the options in this space. TODO: write up
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-a detailed analysis of these languages specifically through the lens of the
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-above goals.
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-
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-One especially interesting aspect not addressed by the active and widely used
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-languages that might serve this purpose is that they have not been designed
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-specifically to enable migration from and interoperability with _today's_ C++.
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-They don't build on top of C++'s _existing_ ecosystem. There are only a few
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-significant examples of programming languages that center around incremental
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-migration of large existing codebases. They are specifically designed to not
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-require complete rewrites, new programming models, or building an entire new
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-stack/ecosystem. However, there is no comparable option for C++ today:
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-
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-- JavaScript → TypeScript
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-- Java → Kotlin
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-- C++ → **???**
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-
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-Carbon explores what it would look like to fill this gap and align it with the
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-above priorities.
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-
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-## Project status
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-
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-**The project is just getting started.** Everything is at a very early stage. If
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-you are hoping to see lots of concrete ideas and plans, you'll probably want to
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-check back in 6 months to a year. At this stage, we're just beginning to lay the
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-foundations.
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-
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-It is important to understand that **this is a science experiment**, not a
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-production effort. There are several initial questions that we want to explore
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-and answer with this experiment:
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-
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-- Can we deliver a design and implementation that is familiar and compelling
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- to C++ programmers and supports our goals?
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-- How seamless and effective can we make interoperability?
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-- How easy and scalable can we make migration?
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-- Will a significant segment of the ecosystem and industry adopt Carbon given
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- these tradeoffs?
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-
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-We are committed to learning the answers to these questions, but that may well
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-not result in a production language. There is a very real chance that this
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-project will never leave the experimental phase. Anyone considering contributing
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-or using Carbon should be extremely mindful of that fact: **core contributors
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-may abandon the experiment**.
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-
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-While we may sometimes refer to Carbon as a language, it is crucial to
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-understand that the goals of this science experiment are not about new
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-languages, but about how to move today's C++ forward effectively. For example, a
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-near optimal outcome would be to convince the C++ community to adopt this as its
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-official path forward.
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-
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-## What will make Carbon a compelling future path for C++?
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-
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-We hope that eventually Carbon will provide **significant advantages compared to
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-today's C++**. Areas where we think we can most dramatically improve C++ for
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-both software systems and developers are:
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-
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-- A cohesive and principled language design, even when supporting advanced
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- features.
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-- Making common coding patterns safe by default whenever practical, with
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- affordable security mitigations available for any unsafety.
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- - We will provide static checks for as many safety issues as we can by
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- default.
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- - We will provide a spectrum of build modes with different trade-offs
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- between dynamic safety and performance. For example:
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- - The default build mode will include as many dynamic safety checks as
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- we can while keeping the software's performance reasonable for
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- normal development, testing, and debugging.
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- - Release builds will favor performance, with opt-in dynamic safety
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- checks and security mitigations for applications with higher
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- security requirements.
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- - Over time, we also expect to both track and drive research into
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- increasing the degree of safety available without compromising our other
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- goals.
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-- Keeping our core language implementation simple, fast, and easily extended
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- in ways that will make all of our language tools better.
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-- Providing an effective, open, and inclusive language evolution process
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- aligned with our goals and priorities.
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-
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-Carbon will also aim to allow a single layer of a legacy C++ library stack to be
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-migrated to Carbon, without migrating the code above or below. This will make it
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-easier for developers to start using Carbon. Key features underpin Carbon's
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-compatibility and interoperability with C++:
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-
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-- The memory, execution, and threading model will be compatible with C++.
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-- Access to existing C++ types, interfaces, and even templates will be
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- provided as part of the core language.
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-- Carbon will be able to export types, interfaces, and templates for
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- consumption by C++.
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-
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-**However, Carbon's approach still requires a nearly complete re-engineering of
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-the language as well as large-scale migration for users.** This is extremely
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-expensive, and so the bar for Carbon to be a compelling direction for C++ is
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-very high.
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-
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-## Contributing
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-
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-Please see our [contributing guidelines](CONTRIBUTING.md) for information about
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-Carbon development.
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+Many languages share these goals, and they can often be addressed independently
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+in a language's design. For the Carbon project, they are prioritized in that
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+order to help make clear what tradeoffs we intend to make.
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+
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+Read the [language overview](docs/design/) for more on the language design
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+itself, and the [goals](docs/project/goals.md) for more on these values.
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+
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+## Carbon and C++
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+
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+If you're already a C++ developer, Carbon should have a short learning curve. It
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+is built out of a consistent set of language constructs that should feel
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+familiar. C++ code like this:
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+
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+<a href="docs/images/snippets.md#c">
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+<img src="docs/images/cpp_snippet.svg" width="600"
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+ alt="A snippet of C++ code. Follow the link to read it.">
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+</a>
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+
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+can be mechanically transformed to Carbon, like so:
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+
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+<a href="docs/images/snippets.md#carbon">
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+<img src="docs/images/carbon_snippet.svg" width="600"
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+ alt="A snippet of converted Carbon code. Follow the link to read it.">
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+</a>
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+
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+without loss of performance or readability. Yet, translating C++ to Carbon isn't
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+necessary; you can call Carbon from C++ without overhead and the other way
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+around. You can port your library to Carbon, or write new Carbon on top of your
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+existing C++ investment. Carbon won't add a sea of dependencies or slow down
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+your performance-critical code. For example:
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+
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+<a href="docs/images/snippets.md#mixed">
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+<img src="docs/images/mixed_snippet.svg" width="600"
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+ alt="A snippet of mixed Carbon and C++ code. Follow the link to read it.">
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+</a>
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+
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+In terms of safety, any language that can seamlessly call C++ will not be
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+perfectly safe in every dimension. However, Carbon's design encourages you to
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+use safe constructs where possible.
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+
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+Ultimately, C++ carries a significant historical legacy, including around ABI
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+stability, that constrains its evolution. Carbon is an attempt to set a new
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+direction for C++ developers that allows for fast development, flexibility, and
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+delight without sacrificing performance, interoperability, and familiarity.
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+
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+Read more about
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+[C++ interop in Carbon](docs/design/interoperability/philosophy_and_goals.md).
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+
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+## Take a look
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+
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+Learn more about Carbon's design:
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+
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+- [Project goals](docs/project/goals.md)
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+- [Language overview](docs/design/)
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+- [Executable semantics](executable_semantics/)
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+
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+## Join us
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+
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+Carbon is committed to a welcoming and inclusive environment where everyone can
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+contribute.
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+
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+- To watch for major release announcements, subscribe to
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+ [our Carbon release post on GitHub](https://github.com/carbon-language/carbon-lang/discussions/1020)
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+ and [star carbon-lang](https://github.com/carbon-language/carbon-lang).
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+- To join the design discussion, join our
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+ [our Github forum](https://github.com/carbon-language/carbon-lang/discussions).
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+- See our [code of conduct](CODE_OF_CONDUCT.md) and
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+ [contributing guidelines](CONTRIBUTING.md) for information about the Carbon
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+ development community.
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+- We discuss Carbon on Discord; a public link will be forthcoming.
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Wolff Dobson
