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Restructure goals doc to reduce nesting. (#1319)
Prior to this change, the section headings for the 7 main goals are visually indistinguishable (in GitHub's rendering) from the boldfaced paragraph headings in those sections. This makes the doc hard to navigate because the structure is hidden.
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Geoff Romer
GitHub
+29
-35
@@ -15,21 +15,19 @@ SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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- [Community and culture](#community-and-culture)
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- [Language tools and ecosystem](#language-tools-and-ecosystem)
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- [Language goals and priorities](#language-goals-and-priorities)
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- [Goals in detail](#goals-in-detail)
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- [Performance-critical software](#performance-critical-software)
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- [Software and language evolution](#software-and-language-evolution)
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- [Code that is easy to read, understand, and write](#code-that-is-easy-to-read-understand-and-write)
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- [Practical safety and testing mechanisms](#practical-safety-and-testing-mechanisms)
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- [Fast and scalable development](#fast-and-scalable-development)
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- [Modern OS platforms, hardware architectures, and environments](#modern-os-platforms-hardware-architectures-and-environments)
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- [Interoperability with and migration from existing C++ code](#interoperability-with-and-migration-from-existing-c-code)
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- [Non-goals](#non-goals)
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- [Stable language and library ABI](#stable-language-and-library-abi)
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- [Backwards or forwards compatibility](#backwards-or-forwards-compatibility)
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- [Legacy compiled libraries without source code or ability to rebuild](#legacy-compiled-libraries-without-source-code-or-ability-to-rebuild)
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- [Support for existing compilation and linking models](#support-for-existing-compilation-and-linking-models)
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- [Idiomatic migration of non-modern, non-idiomatic C++ code](#idiomatic-migration-of-non-modern-non-idiomatic-c-code)
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- [Principles](#principles)
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- [Performance-critical software](#performance-critical-software)
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- [Software and language evolution](#software-and-language-evolution)
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- [Code that is easy to read, understand, and write](#code-that-is-easy-to-read-understand-and-write)
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- [Practical safety and testing mechanisms](#practical-safety-and-testing-mechanisms)
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- [Fast and scalable development](#fast-and-scalable-development)
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- [Modern OS platforms, hardware architectures, and environments](#modern-os-platforms-hardware-architectures-and-environments)
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- [Interoperability with and migration from existing C++ code](#interoperability-with-and-migration-from-existing-c-code)
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- [Non-goals](#non-goals)
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- [Stable language and library ABI](#stable-language-and-library-abi)
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- [Backwards or forwards compatibility](#backwards-or-forwards-compatibility)
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- [Legacy compiled libraries without source code or ability to rebuild](#legacy-compiled-libraries-without-source-code-or-ability-to-rebuild)
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- [Support for existing compilation and linking models](#support-for-existing-compilation-and-linking-models)
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- [Idiomatic migration of non-modern, non-idiomatic C++ code](#idiomatic-migration-of-non-modern-non-idiomatic-c-code)
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- [Prioritization beyond goals](#prioritization-beyond-goals)
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- [Acknowledgements](#acknowledgements)
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@@ -55,6 +53,9 @@ this depends on having high-performance bidirectional interoperability with C++,
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excellent migration tooling, and an easy ramp-up for experienced C++ software
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developers.
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[Principles](principles/README.md) are provided to clarify these goals.
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Principles do not supersede goals and priorities.
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## Project goals
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### Community and culture
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@@ -166,13 +167,11 @@ Many languages share subsets of these goals, but what distinguishes Carbon is
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their combination. Where it is necessary to make tradeoffs between these goals,
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we intend to prioritize them in this order.
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### Goals in detail
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Each goal is broad, and has several facets to consider when making decisions.
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Below, we discuss all of these goals in more detail to give a deeper
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understanding of both the nature and motivation of these goals.
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#### Performance-critical software
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### Performance-critical software
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All software consumes resources: time, memory, compute, power, binary size, and
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so on. In many cases, raw resource usage is not the biggest concern. Instead,
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@@ -210,7 +209,7 @@ brittle baseline performance that cannot be reliably sustained.
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leave the rules and structure of Carbon, whether to gain control over
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performance problems or to gain access to hardware facilities.
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#### Software and language evolution
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### Software and language evolution
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Titus Winters writes in "Non-Atomic Refactoring and Software Sustainability":
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@@ -264,7 +263,7 @@ many options open, such as dedicated and potentially slower features, it does
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limit the degree to which legacy use cases beyond source code should shape the
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Carbon design.
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#### Code that is easy to read, understand, and write
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### Code that is easy to read, understand, and write
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While this is perhaps the least unique among programming languages of the goals
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we list here, we feel it is important to state it, explain all of what we mean
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@@ -364,7 +363,7 @@ make the features easier to understand. It's also often the best way to ensure
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predictable performance, although supporting peak performance may require
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options for more complex implementation behavior.
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#### Practical safety and testing mechanisms
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### Practical safety and testing mechanisms
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Our goal is to add as much language-level safety and security to Carbon as
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possible, using a hybrid strategy to balance other goals. We will do as many
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@@ -397,7 +396,7 @@ this can be seen in facilities that allow indexing into an array: such
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facilities should be designed to have the bounds of the array available to
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implement bounds checking when desirable.
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#### Fast and scalable development
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### Fast and scalable development
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Software development iteration has a critical "edit, test, debug" cycle.
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Developers will use IDEs, editors, compilers, and other tools that need
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@@ -428,7 +427,7 @@ requires separate compilation of source files, and potentially other incremental
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build strategies. Separate compilation also enables better scalability options
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for build systems of large software.
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#### Modern OS platforms, hardware architectures, and environments
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### Modern OS platforms, hardware architectures, and environments
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Carbon must have strong support for all of the major, modern OS platforms, the
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hardware architectures they run on, and the environments in which their software
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@@ -457,7 +456,7 @@ platforms.
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For examples, please see Carbon's
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[success criteria](principles/success_criteria.md#modern-os-platforms-hardware-architectures-and-environments).
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#### Interoperability with and migration from existing C++ code
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### Interoperability with and migration from existing C++ code
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We want developers working within existing C++ ecosystems to easily start using
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Carbon, without starting from scratch. Adopting Carbon should not require
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@@ -511,14 +510,14 @@ given piece code only needs to be migrated once, we expect interoperability to
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be invoked continuously to support migrated code and will thus remain important
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for most developers.
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### Non-goals
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## Non-goals
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There are common or expected goals of many programming languages that we
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explicitly call out as non-goals for Carbon. That doesn't make these things bad
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in any way, but reflects the fact that they do not provide meaningful value to
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us and come with serious costs and/or risks.
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#### Stable language and library ABI
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### Stable language and library ABI
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We would prefer to provide better, dedicated mechanisms to decompose software
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subsystems in ways that scale over time rather than providing a stable ABI
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@@ -543,7 +542,7 @@ or Swift's ["resilience"](https://swift.org/blog/library-evolution/) model. The
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specific approach should be designed around the goals outlined above in order to
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fit the Carbon language.
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#### Backwards or forwards compatibility
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### Backwards or forwards compatibility
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Our goals are focused on _migration_ from one version of Carbon to the next
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rather than _compatibility_ between them. This is rooted in our experience with
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@@ -554,7 +553,7 @@ require some manual intervention despite our best efforts, due to
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[Hyrum's Law](http://www.hyrumslaw.com), and so we should acknowledge that
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upgrades require active migrations.
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#### Legacy compiled libraries without source code or ability to rebuild
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### Legacy compiled libraries without source code or ability to rebuild
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We consider it a non-goal to support legacy code for which the source code is no
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longer available, though we do sympathize with such use cases and would like the
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@@ -563,7 +562,7 @@ Similarly, plugin ABIs aren’t our particular concern, yet we’re interested i
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seeing tooling which can help bridge between programs and plugins which use
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different ABIs.
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#### Support for existing compilation and linking models
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### Support for existing compilation and linking models
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While it is essential to have interoperability with C++, we are willing to
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change the compilation and linking model of C++ itself to enable this if
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@@ -574,7 +573,7 @@ have been implemented thus far in compilers and linkers.
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As a concrete example, Carbon will not support platforms that cannot update
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their compiler and linker alongside the language.
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#### Idiomatic migration of non-modern, non-idiomatic C++ code
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### Idiomatic migration of non-modern, non-idiomatic C++ code
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While large-scale, tool-assisted migration of C++ code to Carbon is an explicit
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goal, handling all C++ code with this is expressly not a goal. There is likely a
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@@ -586,11 +585,6 @@ improving on it is not a goal. Migration support will prioritize code that
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adheres to reasonable C++ best practices, such as avoiding undefined behavior,
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maintaining good test coverage, and validating tests with sanitizers.
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### Principles
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[Principles](principles/README.md) are provided to clarify these goals.
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Principles do not supersede goals and priorities.
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## Prioritization beyond goals
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The features, tools, and other efforts of Carbon should be prioritized based on
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