Proposes a set of core features for declaring and implementing generic
variadic
functions.
A "pack expansion" is a syntactic unit beginning with `...`, which is a
kind of
compile-time loop over sequences called "packs". Packs are initialized
and
referred to using "pack bindings", which are marked with the `each`
keyword at
the point of declaration and the point of use.
The syntax and behavior of a pack expansion depends on its context, and
in some
cases by a keyword following the `...`:
- In a tuple literal expression (such as a function call argument list),
`...`
iteratively evaluates its operand expression, and treats the values as
successive elements of the tuple.
- `...and` and `...or` iteratively evaluate a boolean expression,
combining
the values using `and` and `or`, and ending the loop early if the
underlying
operator short-circuits.
- In a statement context, `...` iteratively executes a statement.
- In a tuple literal pattern (such as a function parameter list), `...`
iteratively matches the elements of the scrutinee tuple. In conjunction
with
pack bindings, this enables functions to take an arbitrary number of
arguments.
---------
Co-authored-by: josh11b <josh11b@users.noreply.github.com>
Co-authored-by: Richard Smith <richard@metafoo.co.uk>
Co-authored-by: josh11b <15258583+josh11b@users.noreply.github.com>
Co-authored-by: Chandler Carruth <chandlerc@gmail.com>
Co-authored-by: Carbon Infra Bot <carbon-external-infra@google.com>
The version of `flake8` was too old to support with Python 3.12 -- there
is new F-string support that caused false positives sadly. The updated
version has fixes for all of these.
This in turn updates codespell which has picked up several new fixes
that actually fire in our code, so also fix everything. While we don't
do more in-depth updates to old proposals, similar to simply fixing
broken links, fixing automatically detected typos seems scalable and
fine.
All edits were automatically generated here.
Use the keyword `impls` instead of `is` when writing a `where` constraint that a type variable needs to implement an interface or named constraint.
What was previously (provisionally) written:
```
fn Sort[T:! Container where .ElementType is Ordered](x: T*);
```
will now be written:
```
fn Sort[T:! Container where .ElementType impls Ordered](x: T*);
```
---------
Co-authored-by: Geoff Romer <gromer@google.com>
Co-authored-by: Chandler Carruth <chandlerc@gmail.com>
The most significant change here is that explorer now uses the chosen spelling
rather than the old `Bool` spelling. Also update a few documentation examples
and some skeletal design docs to use the chosen spelling.
This proposal addresses the question of whether we should perform a fully top-down compilation (like in C), a mostly top-down compilation (like in C++), or whether we should allow information from later in the same source file to be used in earlier program constructs (like in Rust, Swift, Java, C#, Haskell, and so on).
The proposed direction is:
- Entities declared later in the same source file cannot be used earlier; top-down semantics apply everywhere.
- As an exception, class member function bodies are parsed as if they appeared after the class.
- Forward declarations can be used to separate interface from implementation and to allow entities to be used before they are defined.
- The behavior of the program is nonetheless required to be the same as if we had a globally-consistent rule: it's always a hard error to depend on any information that is not known or that is provided later.
This is a proposal to adopt interfaces as the single static open extension mechanism for things like selecting how operators are implemented for types.
Co-authored-by: Richard Smith <richard@metafoo.co.uk>
Establish a principle that understanding the meaning and performance should not depend on expensive context, and explain what makes context expensive.
Co-authored-by: Chandler Carruth <chandlerc@gmail.com>
Co-authored-by: Jon Meow <46229924+jonmeow@users.noreply.github.com>
Co-authored-by: Richard Smith <richard@metafoo.co.uk>
A Carbon function that needs to report recoverable failures should return a sum type whose alternatives represent the success case and failure cases, such as Optional(T), Result(T, Error), or Bool. The function's successful return
value, and any metadata about the failure, should be embedded in the alternatives of the sum type, rather than reported by way of output parameters or other side channels. Carbon's design will prioritize making this form of error handling efficient and ergonomic.
Co-authored-by: josh11b <josh11b@users.noreply.github.com>
Adopts new copyright and markdown toc checks.
The new toc check generates the toc header, so that's why all the md files changed (this had felt better to me for the long-term, more auto-generated content)
We're running into issues with md handlers that expect this kind of 4-space indent. It should be cross-compatible with GH, so switch, even though it feels a little churny.
Manual edits are to:
- .prettierrc.yaml:
- rename from .prettierrc
- add tabWidth (primary change)
- add trailingComma (fix vimPrettier skew)
- contribution_tools.md: Fix remarks about .prettierrc.yaml
- pre-commit-toc.js: indent, bullets
- pre-commit-proposal-list.py: indent of output
The rest is the result of `pre-commit run --all-files`
Unfortunately this'll probably depend on the change being propagated into PR branches, so I wouldn't be surprised if we see regressions for a bit. We'll also need to nudge people to update .vimrc's. Hopefully the pre-commit GH action helps catch issues.
This catches some common spelling errors, but is *not* an exhaustive spell-checker. The only false positive is "rouge" in Gemfile.lock, which is why I'm excluding that file.
True positives are in the change, and it does catch the "langauge" typo I keep making, which zygoloid fixed for me in a few spots. False negatives are:
- virmc
- Announcemented
- propsal
For comparison:
- cspell (https://www.npmjs.com/package/cspell) is too aggressive and has a small dictionary
- Caught the false negatives, but many false positives, including 'LLVM', 'roadmap', 'Carruth'
- https://github.com/lorenzwalthert/precommit has a spellcheck, but config looks ruby-specific
* First draft of a README for the principles/ directory.
* More closely mirror the relevant section from the goals doc.
* Reword bit about excluding using chandlerc@'s suggested text.
* Link to goals doc.
* Update docs/project/principles/README.md
Co-authored-by: Jon Meow <46229924+jonmeow@users.noreply.github.com>
Co-authored-by: Jon Meow <46229924+jonmeow@users.noreply.github.com>
Nathan Youngman
Enzo Venturi
Dennis Onyeka
Jon Ross-Perkins
Josh Soref
Jon Meow
George Kulakowski