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spec: use original terminology in metasyntax (cleanup)
The metasyntax used in the spec is exactly the Wirth Syntax Notation (WSN), which eventually influenced EBNF. Add a link but keep mentioning EBNF which is likely more commonly known. Use the original terms in the productions. Specifically, use the words "Term" and "Factor" rather than "Alternative" and "Term". The terminology cleanup also resolves an inconsistency in the subsequent prose which is referring to the correct "terms" now. While at it, add a production for the entire Syntax itself, matching the original WSN definition. Also, replace the two uses of "grammar" with "syntax" for consistency ("syntax" is the prevalent term used throughout the spec). Fixes #50074. Change-Id: If770d5f32f56f509f85893782c1dafbb0eb29b2e Reviewed-on: https://go-review.googlesource.com/c/go/+/405814 Reviewed-by: Robert Findley <rfindley@google.com> Reviewed-by: Robert Griesemer <gri@google.com> Reviewed-by: Ian Lance Taylor <iant@golang.org>
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@ -22,20 +22,23 @@ dependencies.
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</p>
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<p>
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The grammar is compact and simple to parse, allowing for easy analysis
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The syntax is compact and simple to parse, allowing for easy analysis
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by automatic tools such as integrated development environments.
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</p>
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<h2 id="Notation">Notation</h2>
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<p>
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The syntax is specified using Extended Backus-Naur Form (EBNF):
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The syntax is specified using a
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<a href="https://en.wikipedia.org/wiki/Wirth_syntax_notation">variant</a>
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of Extended Backus-Naur Form (EBNF):
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</p>
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<pre class="grammar">
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Syntax = { Production } .
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Production = production_name "=" [ Expression ] "." .
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Expression = Alternative { "|" Alternative } .
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Alternative = Term { Term } .
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Term = production_name | token [ "…" token ] | Group | Option | Repetition .
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Expression = Term { "|" Term } .
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Term = Factor { Factor } .
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Factor = production_name | token [ "…" token ] | Group | Option | Repetition .
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Group = "(" Expression ")" .
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Option = "[" Expression "]" .
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Repetition = "{" Expression "}" .
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@ -53,7 +56,7 @@ operators, in increasing precedence:
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</pre>
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<p>
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Lowercase production names are used to identify lexical tokens.
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Lowercase production names are used to identify lexical (terminal) tokens.
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Non-terminals are in CamelCase. Lexical tokens are enclosed in
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double quotes <code>""</code> or back quotes <code>``</code>.
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</p>
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@ -170,7 +173,7 @@ valid token.
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<h3 id="Semicolons">Semicolons</h3>
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<p>
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The formal grammar uses semicolons <code>";"</code> as terminators in
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The formal syntax uses semicolons <code>";"</code> as terminators in
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a number of productions. Go programs may omit most of these semicolons
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using the following two rules:
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</p>
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@ -3038,7 +3041,7 @@ Element = Expression | LiteralValue .
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<p>
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The LiteralType's <a href="#Core_types">core type</a> <code>T</code>
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must be a struct, array, slice, or map type
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(the grammar enforces this constraint except when the type is given
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(the syntax enforces this constraint except when the type is given
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as a TypeName).
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The types of the elements and keys must be <a href="#Assignability">assignable</a>
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to the respective field, element, and key types of type <code>T</code>;
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