This module contains an internal syntax that's used to represent documents.

Ordinarily, a syntax declaration is used to extend the Lean parser. The parser produces Syntax, which is flexible enough to represent essentially anything. However, each syntax declaration will produce parsed syntax trees with a predictable form, and these syntax trees can be matched using quasiquotation patterns. In other words, syntax declarations really do all of the following:

• They extend Lean's parser
• They establish expectations for valid subsets of Syntax
• They provide a way to pattern-match against the valid Syntax that they induce

The syntax declarations in this module are used somewhat differently. They're not generally intended for direct use with the Lean parser, because the concrete syntax of Verso documents falls outside what can be implemented with Lean's parsing framework. Thus, Verso has a separate parser, written using the lower-level parts of Lean's parser. These syntax declarations are, however, a specification for the syntax trees produced by said parser. The Verso parser is in the module Lean.DocString.Parser. Specifying the Verso document syntax as is done here also allows quasiquotation patterns that match against the output of the Verso parser.

Importantly, Lean quasiquotation patterns do not match the string contents of atoms. This means that the Verso parser may produce a node of kind `Lean.Doc.Syntax.li in which the first atom is "1." rather than "*' when parsing an ordered list.

Parsed Verso documents are transformed into Lean syntax that represents Verso document ASTs (see module Lean.DocString.Types). This process potentially invokes user-written metaprograms - while Verso's concrete syntax is not extensible, roles, directives and code blocks all contain explicit hooks for extensibility. This translation step is defined in the module Lean.DocString.Elab.

def Lean.Parser.Category.arg_val : Category

Argument values

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• Lean.Parser.Category.arg_val = { }

def Lean.Doc.Syntax.arg_val.quot : ParserDescr

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def Lean.Doc.Syntax.arg_str : ParserDescr

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• Lean.Doc.Syntax.arg_str = Lean.ParserDescr.node `Lean.Doc.Syntax.arg_str 1022 (Lean.ParserDescr.const `str)

def Lean.Doc.Syntax.arg_ident : ParserDescr

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• Lean.Doc.Syntax.arg_ident = Lean.ParserDescr.node `Lean.Doc.Syntax.arg_ident 1022 (Lean.ParserDescr.const `ident)

def Lean.Doc.Syntax.arg_num : ParserDescr

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• Lean.Doc.Syntax.arg_num = Lean.ParserDescr.node `Lean.Doc.Syntax.arg_num 1022 (Lean.ParserDescr.const `num)

def Lean.Parser.Category.doc_arg : Category

Arguments

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• Lean.Parser.Category.doc_arg = { }

def Lean.Doc.Syntax.doc_arg.quot : ParserDescr

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def Lean.Doc.Syntax.anon : ParserDescr

Anonymous positional argument

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• Lean.Doc.Syntax.anon = Lean.ParserDescr.node `Lean.Doc.Syntax.anon 1022 (Lean.ParserDescr.cat `arg_val 0)

def Lean.Doc.Syntax.named : ParserDescr

Named argument

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def Lean.Doc.Syntax.named_no_paren : ParserDescr

Named argument

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def Lean.Doc.Syntax.flag_on : ParserDescr

Boolean flag, turned on

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• Lean.Doc.Syntax.flag_on = Lean.ParserDescr.node `Lean.Doc.Syntax.flag_on 1022 (Lean.ParserDescr.binary `andthen (Lean.ParserDescr.symbol "+") (Lean.ParserDescr.const `ident))

def Lean.Doc.Syntax.flag_off : ParserDescr

Boolean flag, turned off

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• Lean.Doc.Syntax.flag_off = Lean.ParserDescr.node `Lean.Doc.Syntax.flag_off 1022 (Lean.ParserDescr.binary `andthen (Lean.ParserDescr.symbol "-") (Lean.ParserDescr.const `ident))

def Lean.Parser.Category.link_target : Category

Link targets, which may be URLs or named references

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• Lean.Parser.Category.link_target = { }

def Lean.Doc.Syntax.link_target.quot : ParserDescr

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def Lean.Doc.Syntax.url : ParserDescr

A URL target, written explicitly. Use square brackets for a named target.

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def Lean.Doc.Syntax.ref : ParserDescr

A named reference to a URL defined elsewhere. Use parentheses to write the URL here.

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def Lean.Parser.Category.inline : Category

Verso inline objects. These are part of the ordinary text flow of a paragraph.

This syntax uses the following conventions:

• Sequences of inline items are in square brackets
• Literal data, like strings or numbers, are in parentheses
• Verso metaprogram names and arguments are in curly braces

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• Lean.Parser.Category.inline = { }

def Lean.Doc.Syntax.inline.quot : ParserDescr

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def Lean.Doc.Syntax.text : ParserDescr

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• Lean.Doc.Syntax.text = Lean.ParserDescr.node `Lean.Doc.Syntax.text 1022 (Lean.ParserDescr.const `str)

def Lean.Doc.Syntax.emph : ParserDescr

Emphasis, often rendered as italics.

Emphasis may be nested by using longer sequences of _ for the outer delimiters. For example:

Remember: __always butter the _rugbrød_ before adding toppings!__

Here, the outer __ is used to emphasize the instructions, while the inner _ indicates the use of a non-English word.

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def Lean.Doc.Syntax.bold : ParserDescr

Bold emphasis.

A single * suffices to make text bold. Using _ for emphasis.

Bold text may be nested by using longer sequences of * for the outer delimiters.

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def Lean.Doc.Syntax.link : ParserDescr

A link. The link's target may either be a concrete URL (written in parentheses) or a named URL (written in square brackets).

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def Lean.Doc.Syntax.image : ParserDescr

An image, with alternate text and a URL.

The alternate text is a plain string, rather than Verso markup.

The image URL may either be a concrete URL (written in parentheses) or a named URL (written in square brackets).

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def Lean.Doc.Syntax.footnote : ParserDescr

A footnote use site.

Footnotes must be defined elsewhere using the [^NAME]: TEXT syntax.

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def Lean.Doc.Syntax.linebreak : ParserDescr

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• Lean.Doc.Syntax.linebreak = Lean.ParserDescr.node `Lean.Doc.Syntax.linebreak 1022 (Lean.ParserDescr.binary `andthen (Lean.ParserDescr.symbol "line!") (Lean.ParserDescr.const `str))

def Lean.Doc.Syntax.code : ParserDescr

Literal code.

Code may begin with any non-zero number of backticks. It must be terminated with the same number, and it may not contain a sequence of backticks that is at least as long as its starting or ending delimiters.

If the first and last characters are space, and it contains at least one non-space character, then the resulting string has a single space stripped from each end. Thus, `` `x `` represents "`x", not " `x ".

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def Lean.Doc.Syntax.role : ParserDescr

A role: an extension to the Verso document language in an inline position.

Text is given a role using the following syntax: {NAME ARGS*}[CONTENT]. The NAME is an identifier that determines which role is being used, akin to a function name. Each of the ARGS may have the following forms:

• A value, which is a string literal, natural number, or identifier
• A named argument, of the form (NAME := VALUE)
• A flag, of the form +NAME or -NAME

The CONTENT is a sequence of inline content. If there is only one piece of content and it has beginning and ending delimiters (e.g. code literals, links, or images, but not ordinary text), then the [ and ] may be omitted. In particular, {NAME ARGS*}`x` is equivalent to {NAME ARGS*}[`x`].

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def Lean.Doc.Syntax.inline_math : ParserDescr

Inline mathematical notation (equivalent to LaTeX's $ notation)

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• Lean.Doc.Syntax.inline_math = Lean.ParserDescr.node `Lean.Doc.Syntax.inline_math 1022 (Lean.ParserDescr.binary `andthen (Lean.ParserDescr.symbol "\\math") Lean.Doc.Syntax.code)

def Lean.Doc.Syntax.display_math : ParserDescr

Display-mode mathematical notation

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• Lean.Doc.Syntax.display_math = Lean.ParserDescr.node `Lean.Doc.Syntax.display_math 1022 (Lean.ParserDescr.binary `andthen (Lean.ParserDescr.symbol "\\displaymath") Lean.Doc.Syntax.code)

def Lean.Parser.Category.block : Category

Block-level elements, such as paragraphs, headers, and lists.

Conventions:

• When there's concrete syntax that can be written as Lean atoms, do so (code blocks are ```, directives :::)
• When Verso's syntax requires a newline, use | because "\n" is not a valid Lean token
• Directive bodies are in { and } to avoid quotation parsing issues with ::: ... :::
• If there's no concrete syntax per se, such as for paragraphs or lists, use a name with brackets and braces
• Use parentheses around required literals, such as the starting number of an ordered list
• Use square brackets around sequences of literals
• Use curly braces around blocks or lists items (because names and arguments a la roles are always newline-separated for directives and code)

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• Lean.Parser.Category.block = { }

def Lean.Doc.Syntax.block.quot : ParserDescr

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def Lean.Parser.Category.list_item : Category

Items from both ordered and unordered lists

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• Lean.Parser.Category.list_item = { }

def Lean.Doc.Syntax.list_item.quot : ParserDescr

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def Lean.Doc.Syntax.li : ParserDescr

A list item

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def Lean.Parser.Category.desc_item : Category

A description of an item

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• Lean.Parser.Category.desc_item = { }

def Lean.Doc.Syntax.desc_item.quot : ParserDescr

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def Lean.Doc.Syntax.desc : ParserDescr

A description of an item

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def Lean.Doc.Syntax.para : ParserDescr

Paragraph

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def Lean.Doc.Syntax.ul : ParserDescr

Unordered List

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def Lean.Doc.Syntax.dl : ParserDescr

Description list

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def Lean.Doc.Syntax.ol : ParserDescr

Ordered list

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def Lean.Doc.Syntax.codeblock : ParserDescr

A code block that contains literal code.

Code blocks have the following syntax:

```(NAME ARGS*)?
CONTENT
```

CONTENT is a literal string. If the CONTENT contains a sequence of three or more backticks, then the opening and closing ``` (called fences) should have more backticks than the longest sequence in CONTENT. Additionally, the opening and closing fences should have the same number of backticks.

If NAME and ARGS are not provided, then the code block represents literal text. If provided, the NAME is an identifier that selects an interpretation of the block. Unlike Markdown, this name is not necessarily the language in which the code is written, though many custom code blocks are, in practice, named after the language that they contain. NAME is more akin to a function name. Each of the ARGS may have the following forms:

• A value, which is a string literal, natural number, or identifier
• A named argument, of the form (NAME := VALUE)
• A flag, of the form +NAME or -NAME

The CONTENT is interpreted according to the indentation of the fences. If the fences are indented n spaces, then n spaces are removed from the start of each line of CONTENT.

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def Lean.Doc.Syntax.blockquote : ParserDescr

A quotation, which contains a sequence of blocks that are at least as indented as the >.

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def Lean.Doc.Syntax.link_ref : ParserDescr

A named URL that can be used in links and images.

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def Lean.Doc.Syntax.footnote_ref : ParserDescr

A footnote definition.

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def Lean.Doc.Syntax.directive : ParserDescr

A directive, which is an extension to the Verso language in block position.

Directives have the following syntax:

:::NAME ARGS*
CONTENT*
:::

The NAME is an identifier that determines which directive is being used, akin to a function name. Each of the ARGS may have the following forms:

• A value, which is a string literal, natural number, or identifier
• A named argument, of the form (NAME := VALUE)
• A flag, of the form +NAME or -NAME

The CONTENT is a sequence of block content. Directives may be nested by using more colons in the outer directive. For example:

::::outer +flag (arg := 5)
A paragraph.
:::inner "label"
* 1
* 2
:::
::::

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def Lean.Doc.Syntax.header : ParserDescr

A header

Headers must be correctly nested to form a tree structure. The first header in a document must start with #, and subsequent headers must have at most one more # than the preceding header.

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def Lean.Doc.Syntax.metadataContents : Parser.Parser

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• Lean.Doc.Syntax.metadataContents = Lean.Parser.Term.structInstFields (Lean.Parser.sepByIndent Lean.Parser.Term.structInstField ", " (Lean.Parser.symbol ", ") true)

def Lean.Doc.Syntax.metadata_block : ParserDescr

Metadata for the preceding header.

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def Lean.Doc.Syntax.command : ParserDescr

A block-level command, which invokes an extension during documentation processing.

The NAME is an identifier that determines which command is being used, akin to a function name. Each of the ARGS may have the following forms:

• A value, which is a string literal, natural number, or identifier
• A named argument, of the form (NAME := VALUE)
• A flag, of the form +NAME or -NAME

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