50 lines
1.7 KiB
Markdown
50 lines
1.7 KiB
Markdown
---
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title: "Canonical Form for Binary Syntax"
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---
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[spec]: preserves.html
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When two `Value`s are written down in *canonical form*, comparing
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their *syntax* for equivalence gives the same result as comparing them
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*semantically* according to the equivalence defined in the
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[Preserves specification][spec].[^equivalence-not-ordering]
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[^equivalence-not-ordering]: However, canonical form does *not*
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induce a match between lexicographic ordering on syntax and
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semantic ordering [as specified][spec]. It *only* induces a
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connection between equivalences.
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That is, canonical forms are equal if and only if the encoded `Value`s
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are equal.
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This document specifies canonical form for the Preserves compact
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binary syntax.
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**General rules.**
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Streaming formats ("format C") *MUST NOT* be used.
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Annotations *MUST NOT* be present.
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Whenever there is a choice between fixed-length ("format A") or
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variable-length ("format B") formats, the fixed-length format *MUST* be
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used.
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**Sets.**
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The elements of a `Set` *MUST* be serialized sorted in ascending order
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following the total order relation defined in the
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[Preserves specification][spec].
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**Dictionaries.**
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The key-value pairs in a `Dictionary` *MUST* be serialized sorted in
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ascending order by key, following the total order relation defined in
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the [Preserves specification][spec].[^no-need-for-by-value]
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[^no-need-for-by-value]: There is no need to order by (key, value)
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pair, since a `Dictionary` has no duplicate keys.
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**Other kinds of `Value`.**
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There are no special canonicalization restrictions on
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`SignedInteger`s, `String`s, `ByteString`s, `Symbol`s, `Boolean`s,
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`Float`s, `Double`s, `Record`s, or `Sequence`s.
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<!-- Heading to visually offset the footnotes from the main document: -->
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## Notes
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