Editorial: Rework the 'Identity' section #3217
Open
Conversation
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
| </ul> | ||
| </li> | ||
| </ul> | ||
| <p><dfn id="language-identity">Language identity</dfn> is identity as seen from the perspective of ECMAScript code. There, language values can be compared for equality in various ways, but the most discriminating is the `Object.is` built-in function, whose semantics are given by the SameValue abstract operation and the abstract operations it transitively calls. These semantics are such that, to a first approximation, language identity matches specification identity. In fact, the only difference between the two involves Symbol values: whereas all Symbols have specification identity, Symbols produced by <emu-xref href="#sec-symbol.for">Symbol.for</emu-xref> do not have language identity.</p> |
There was a problem hiding this comment.
Suggested change
| <p><dfn id="language-identity">Language identity</dfn> is identity as seen from the perspective of ECMAScript code. There, language values can be compared for equality in various ways, but the most discriminating is the `Object.is` built-in function, whose semantics are given by the SameValue abstract operation and the abstract operations it transitively calls. These semantics are such that, to a first approximation, language identity matches specification identity. In fact, the only difference between the two involves Symbol values: whereas all Symbols have specification identity, Symbols produced by <emu-xref href="#sec-symbol.for">Symbol.for</emu-xref> do not have language identity.</p> | |
| <p><dfn id="language-identity">Language identity</dfn> is identity as seen from the perspective of ECMAScript code. All values with language identity have specification identity. The only values with specification identity which do not have language identity are Symbols produced by <emu-xref href="#sec-symbol.for">Symbol.for</emu-xref>. Language identity is used by ECMAScript code through the built-in equality comparison operations.</p> |
There was a problem hiding this comment.
I can live with this suggested rewording.
syg
approved these changes
Dec 6, 2023
| <p>From the perspective of the ECMAScript language, language values are compared for equality using the SameValue abstract operation and the abstract operations it transitively calls. The algorithms of these comparison abstract operations determine <em>language identity</em> of ECMAScript language values.</p> | ||
| <p>For specification values, examples of values without specification identity include, but are not limited to: mathematical values and extended mathematical values; ECMAScript source text, surrogate pairs, Directive Prologues, etc; UTF-16 code units; Unicode code points; enums; abstract operations, including syntax-directed operations, host hooks, etc; and ordered pairs. Examples of specification values with specification identity include, but are not limited to: any kind of Records, including Property Descriptors, PrivateElements, etc; Parse Nodes; Lists; <emu-xref href="#sec-set-and-relation-specification-type">Sets</emu-xref> and Relations; Abstract Closures; Data Blocks; Private Names; execution contexts and execution context stacks; agent signifiers; and WaiterList Records.</p> | ||
| <p>Specification identity agrees with language identity for all ECMAScript language values except Symbol values produced by <emu-xref href="#sec-symbol.for">Symbol.for</emu-xref>. The ECMAScript language values without specification identity and without language identity are <emu-xref href="#sec-ecmascript-language-types-undefined-type">*undefined*</emu-xref>, <emu-xref href="#sec-ecmascript-language-types-null-type">*null*</emu-xref>, <emu-xref href="#sec-ecmascript-language-types-boolean-type">Booleans</emu-xref>, <emu-xref href="#sec-ecmascript-language-types-string-type">Strings</emu-xref>, <emu-xref href="#sec-ecmascript-language-types-number-type">Numbers</emu-xref>, and <emu-xref href="#sec-ecmascript-language-types-bigint-type">BigInts</emu-xref>. The ECMAScript language values with specification identity and language identity are <emu-xref href="#sec-ecmascript-language-types-symbol-type">Symbols</emu-xref> not produced by <emu-xref href="#sec-symbol.for">Symbol.for</emu-xref> and <emu-xref href="#sec-object-type">Objects</emu-xref>. Symbol values produced by <emu-xref href="#sec-symbol.for">Symbol.for</emu-xref> have specification identity, but not language identity.</p> | ||
| <p>To some extent, which values have identity depends on perspective, so we distinguish <em>specification identity</em> and <em>language identity</em>.</p> |
There was a problem hiding this comment.
Suggested change
| <p>To some extent, which values have identity depends on perspective, so we distinguish <em>specification identity</em> and <em>language identity</em>.</p> | |
| <p>Which values have identity depends on perspective, so we distinguish <em>specification identity</em> and <em>language identity</em>.</p> |
I don't think "to some extent" adds anything.
| </ul> | ||
| </li> | ||
| </ul> | ||
| <p><dfn id="language-identity">Language identity</dfn> is identity as seen from the perspective of ECMAScript code. There, language values can be compared for equality in various ways, but the most discriminating is the `Object.is` built-in function, whose semantics are given by the SameValue abstract operation and the abstract operations it transitively calls. These semantics are such that, to a first approximation, language identity matches specification identity. In fact, the only difference between the two involves Symbol values: whereas all Symbols have specification identity, Symbols produced by <emu-xref href="#sec-symbol.for">Symbol.for</emu-xref> do not have language identity.</p> |
There was a problem hiding this comment.
I can live with this suggested rewording.
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
This PR reworks the Identity section (without touching para 1). I don't think it does anything radical to the idea of identity, it just addresses some wording/exposition questions I raised in issue #3207, and also a few other nits I have with the status quo:
Resolves #3207, I think.