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Introduce a concrete design for how Carbon values, objects, storage,
variables,
and pointers will work. This includes fleshing out the design for:
- The expression categories used in Carbon to represent values and
objects,
how they interact, and terminology that anchors on their expression
nature.
- An expression category model for readonly, abstract values that can
efficiently support function inputs.
- A customization system for value expression representations,
especially as
seen on function boundaries in the calling convention.
- An expression category model for references instead of a type system
model.
- How patterns match different expression categories.
- How initialization works in conjunction with function returns.
- Specific pointer syntax, semantics, and library customization
mechanisms.
- A `const` type qualifier for use when the value expression category
system
is too abstracted from the underlying objects in storage.
---------
Co-authored-by: Geoff Romer <gromer@google.com>
Co-authored-by: josh11b <josh11b@users.noreply.github.com>
Co-authored-by: Adrien Leravat <Pixep@users.noreply.github.com>
Co-authored-by: Jon Ross-Perkins <jperkins@google.com>
Co-authored-by: Richard Smith <richard@metafoo.co.uk>
58 lines
1.8 KiB
Markdown
58 lines
1.8 KiB
Markdown
# Pointer operators
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Part of the Carbon Language project, under the Apache License v2.0 with LLVM
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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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## Table of contents
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- [Overview](#overview)
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- [Details](#details)
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- [Precedence](#precedence)
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- [Alternatives considered](#alternatives-considered)
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- [References](#references)
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<!-- tocstop -->
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## Overview
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Carbon provides the following operators related to pointers:
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- `&` as a prefix unary operator takes the address of an object, forming a
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pointer to it.
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- `*` as a prefix unary operator dereferences a pointer.
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Note that [member access expressions](member_access.md) include an `->` form
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that implicitly performs a dereference in the same way as the `*` operator.
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## Details
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The semantic details of pointer operators are collected in the main
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[pointers](/docs/design/values.md#pointers) design. The syntax and precedence
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details are covered here.
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The syntax tries to remain as similar as possible to C++ pointer types as they
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are commonly written in code and are expected to be extremely common and a key
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anchor of syntactic similarity between the languages.
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### Precedence
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These operators have high precedence. Only [member access](member_access.md)
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expressions can be used as an unparenthesized operand to them.
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The two prefix operators `&` and `*` are generally above the other unary and
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binary operators and can appear inside them as unparenthesized operands. For the
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full details, see the [precedence graph](README.md#precedence).
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## Alternatives considered
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- [Alternative pointer syntaxes](/proposals/p2006.md#alternative-pointer-syntaxes)
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## References
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- [Proposal #2006: Values, variables, and pointers](/proposals/p2006.md)
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