Theory Document_Preparation

theory Document_Preparation
imports Base Main
(*:maxLineLen=78:*)

theory Document_Preparation
imports Base Main
begin

chapter ‹Document preparation \label{ch:document-prep}›

text ‹
  Isabelle/Isar provides a simple document preparation system based on
  {PDF-\LaTeX}, with support for hyperlinks and bookmarks within that format.
  This allows to produce papers, books, theses etc.\ from Isabelle theory
  sources.

  {\LaTeX} output is generated while processing a ∗‹session› in batch mode, as
  explained in the ∗‹The Isabelle System Manual› @{cite "isabelle-system"}.
  The main Isabelle tools to get started with document preparation are
  @{tool_ref mkroot} and @{tool_ref build}.

  The classic Isabelle/HOL tutorial @{cite "isabelle-hol-book"} also explains
  some aspects of theory presentation.
›


section ‹Markup commands \label{sec:markup}›

text ‹
  \begin{matharray}{rcl}
    @{command_def "chapter"} & : & ‹any → any› \\
    @{command_def "section"} & : & ‹any → any› \\
    @{command_def "subsection"} & : & ‹any → any› \\
    @{command_def "subsubsection"} & : & ‹any → any› \\
    @{command_def "paragraph"} & : & ‹any → any› \\
    @{command_def "subparagraph"} & : & ‹any → any› \\
    @{command_def "text"} & : & ‹any → any› \\
    @{command_def "txt"} & : & ‹any → any› \\
    @{command_def "text_raw"} & : & ‹any → any› \\
  \end{matharray}

  Markup commands provide a structured way to insert text into the document
  generated from a theory. Each markup command takes a single @{syntax text}
  argument, which is passed as argument to a corresponding {\LaTeX} macro. The
  default macros provided by @{file "~~/lib/texinputs/isabelle.sty"} can be
  redefined according to the needs of the underlying document and {\LaTeX}
  styles.

  Note that formal comments (\secref{sec:comments}) are similar to markup
  commands, but have a different status within Isabelle/Isar syntax.

  @{rail ‹
    (@@{command chapter} | @@{command section} | @@{command subsection} |
      @@{command subsubsection} | @@{command paragraph} | @@{command subparagraph} |
      @@{command text} | @@{command txt} | @@{command text_raw}) @{syntax text}
  ›}

    ➧ @{command chapter}, @{command section}, @{command subsection} etc.\ mark
    section headings within the theory source. This works in any context, even
    before the initial @{command theory} command. The corresponding {\LaTeX}
    macros are ▩‹\isamarkupchapter›, ▩‹\isamarkupsection›,
    ▩‹\isamarkupsubsection› etc.\

    ➧ @{command text} and @{command txt} specify paragraphs of plain text.
    This corresponds to a {\LaTeX} environment ▩‹\begin{isamarkuptext}› ‹…›
    ▩‹\end{isamarkuptext}› etc.

    ➧ @{command text_raw} is similar to @{command text}, but without any
    surrounding markup environment. This allows to inject arbitrary {\LaTeX}
    source into the generated document.

  All text passed to any of the above markup commands may refer to formal
  entities via ∗‹document antiquotations›, see also \secref{sec:antiq}. These
  are interpreted in the present theory or proof context.

  ┉
  The proof markup commands closely resemble those for theory specifications,
  but have a different formal status and produce different {\LaTeX} macros.
›


section ‹Document antiquotations \label{sec:antiq}›

text ‹
  \begin{matharray}{rcl}
    @{antiquotation_def "theory"} & : & ‹antiquotation› \\
    @{antiquotation_def "thm"} & : & ‹antiquotation› \\
    @{antiquotation_def "lemma"} & : & ‹antiquotation› \\
    @{antiquotation_def "prop"} & : & ‹antiquotation› \\
    @{antiquotation_def "term"} & : & ‹antiquotation› \\
    @{antiquotation_def term_type} & : & ‹antiquotation› \\
    @{antiquotation_def typeof} & : & ‹antiquotation› \\
    @{antiquotation_def const} & : & ‹antiquotation› \\
    @{antiquotation_def abbrev} & : & ‹antiquotation› \\
    @{antiquotation_def typ} & : & ‹antiquotation› \\
    @{antiquotation_def type} & : & ‹antiquotation› \\
    @{antiquotation_def class} & : & ‹antiquotation› \\
    @{antiquotation_def "text"} & : & ‹antiquotation› \\
    @{antiquotation_def goals} & : & ‹antiquotation› \\
    @{antiquotation_def subgoals} & : & ‹antiquotation› \\
    @{antiquotation_def prf} & : & ‹antiquotation› \\
    @{antiquotation_def full_prf} & : & ‹antiquotation› \\
    @{antiquotation_def ML} & : & ‹antiquotation› \\
    @{antiquotation_def ML_op} & : & ‹antiquotation› \\
    @{antiquotation_def ML_type} & : & ‹antiquotation› \\
    @{antiquotation_def ML_structure} & : & ‹antiquotation› \\
    @{antiquotation_def ML_functor} & : & ‹antiquotation› \\
    @{antiquotation_def emph} & : & ‹antiquotation› \\
    @{antiquotation_def bold} & : & ‹antiquotation› \\
    @{antiquotation_def verbatim} & : & ‹antiquotation› \\
    @{antiquotation_def "file"} & : & ‹antiquotation› \\
    @{antiquotation_def "url"} & : & ‹antiquotation› \\
    @{antiquotation_def "cite"} & : & ‹antiquotation› \\
    @{command_def "print_antiquotations"}‹*› & : & ‹context →› \\
  \end{matharray}

  The overall content of an Isabelle/Isar theory may alternate between formal
  and informal text. The main body consists of formal specification and proof
  commands, interspersed with markup commands (\secref{sec:markup}) or
  document comments (\secref{sec:comments}). The argument of markup commands
  quotes informal text to be printed in the resulting document, but may again
  refer to formal entities via ∗‹document antiquotations›.

  For example, embedding ▩‹@{term [show_types] "f x = a + x"}›
  within a text block makes
  \isa{{\isacharparenleft}f{\isasymColon}{\isacharprime}a\ {\isasymRightarrow}\ {\isacharprime}a{\isacharparenright}\ {\isacharparenleft}x{\isasymColon}{\isacharprime}a{\isacharparenright}\ {\isacharequal}\ {\isacharparenleft}a{\isasymColon}{\isacharprime}a{\isacharparenright}\ {\isacharplus}\ x} appear in the final {\LaTeX} document.

  Antiquotations usually spare the author tedious typing of logical entities
  in full detail. Even more importantly, some degree of consistency-checking
  between the main body of formal text and its informal explanation is
  achieved, since terms and types appearing in antiquotations are checked
  within the current theory or proof context.

  ┉
  Antiquotations are in general written as
  ▩‹@{›‹name›~▩‹[›‹options›▩‹]›~‹arguments›▩‹}›. The short form
  ▩‹\›▩‹<^›‹name›▩‹>›‹‹argument_content›› (without surrounding ▩‹@{›‹…›▩‹}›)
  works for a single argument that is a cartouche. A cartouche without special
  decoration is equivalent to ▩‹\<^cartouche>›‹‹argument_content››, which is
  equivalent to ▩‹@{cartouche›~‹‹argument_content››▩‹}›. The special name
  @{antiquotation_def cartouche} is defined in the context: Isabelle/Pure
  introduces that as an alias to @{antiquotation_ref text} (see below).
  Consequently, ‹‹foo_bar + baz ≤ bazar›› prints literal quasi-formal text
  (unchecked). A control symbol ▩‹\›▩‹<^›‹name›▩‹>› within the body text, but
  without a subsequent cartouche, is equivalent to ▩‹@{›‹name›▩‹}›.

  \begingroup
  \def\isasymcontrolstart{\isatt{\isacharbackslash\isacharless\isacharcircum}}
  @{rail ‹
    @{syntax_def antiquotation}:
      '@{' antiquotation_body '}' |
      '\<controlstart>' @{syntax_ref name} '>' @{syntax_ref cartouche} |
      @{syntax_ref cartouche}
    ;
    options: '[' (option * ',') ']'
    ;
    option: @{syntax name} | @{syntax name} '=' @{syntax name}
    ;
  ›}
  \endgroup

  Note that the syntax of antiquotations may ∗‹not› include source comments
  ▩‹(*›~‹…›~▩‹*)› nor verbatim text ▩‹{*›~‹…›~▩‹*}›.

  %% FIXME less monolithic presentation, move to individual sections!?
  @{rail ‹
    @{syntax_def antiquotation_body}:
      (@@{antiquotation text} | @@{antiquotation cartouche} | @@{antiquotation theory_text})
        options @{syntax text} |
      @@{antiquotation theory} options @{syntax name} |
      @@{antiquotation thm} options styles @{syntax thmrefs} |
      @@{antiquotation lemma} options @{syntax prop} @'by' @{syntax method} @{syntax method}? |
      @@{antiquotation prop} options styles @{syntax prop} |
      @@{antiquotation term} options styles @{syntax term} |
      @@{antiquotation (HOL) value} options styles @{syntax term} |
      @@{antiquotation term_type} options styles @{syntax term} |
      @@{antiquotation typeof} options styles @{syntax term} |
      @@{antiquotation const} options @{syntax term} |
      @@{antiquotation abbrev} options @{syntax term} |
      @@{antiquotation typ} options @{syntax type} |
      @@{antiquotation type} options @{syntax name} |
      @@{antiquotation class} options @{syntax name} |
      (@@{antiquotation command} | @@{antiquotation method} | @@{antiquotation attribute})
        options @{syntax name}
    ;
    @{syntax antiquotation}:
      @@{antiquotation goals} options |
      @@{antiquotation subgoals} options |
      @@{antiquotation prf} options @{syntax thmrefs} |
      @@{antiquotation full_prf} options @{syntax thmrefs} |
      @@{antiquotation ML} options @{syntax text} |
      @@{antiquotation ML_op} options @{syntax text} |
      @@{antiquotation ML_type} options @{syntax text} |
      @@{antiquotation ML_structure} options @{syntax text} |
      @@{antiquotation ML_functor} options @{syntax text} |
      @@{antiquotation emph} options @{syntax text} |
      @@{antiquotation bold} options @{syntax text} |
      @@{antiquotation verbatim} options @{syntax text} |
      @@{antiquotation "file"} options @{syntax name} |
      @@{antiquotation file_unchecked} options @{syntax name} |
      @@{antiquotation url} options @{syntax name} |
      @@{antiquotation cite} options @{syntax cartouche}? (@{syntax name} + @'and')
    ;
    styles: '(' (style + ',') ')'
    ;
    style: (@{syntax name} +)
    ;
    @@{command print_antiquotations} ('!'?)
  ›}

  ➧ ‹@{text s}› prints uninterpreted source text ‹s›, i.e.\ inner syntax. This
  is particularly useful to print portions of text according to the Isabelle
  document style, without demanding well-formedness, e.g.\ small pieces of
  terms that should not be parsed or type-checked yet.

  It is also possible to write this in the short form ‹‹s›› without any
  further decoration.

  ➧ ‹@{theory_text s}› prints uninterpreted theory source text ‹s›, i.e.\
  outer syntax with command keywords and other tokens.

  ➧ ‹@{theory A}› prints the name ‹A›, which is guaranteed to refer to a valid
  ancestor theory in the current context.

  ➧ ‹@{thm a1 … an}› prints theorems ‹a1 … an›. Full fact expressions are
  allowed here, including attributes (\secref{sec:syn-att}).

  ➧ ‹@{prop φ}› prints a well-typed proposition ‹φ›.

  ➧ ‹@{lemma φ by m}› proves a well-typed proposition ‹φ› by method ‹m› and
  prints the original ‹φ›.

  ➧ ‹@{term t}› prints a well-typed term ‹t›.
  
  ➧ ‹@{value t}› evaluates a term ‹t› and prints its result, see also
  @{command_ref (HOL) value}.

  ➧ ‹@{term_type t}› prints a well-typed term ‹t› annotated with its type.

  ➧ ‹@{typeof t}› prints the type of a well-typed term ‹t›.

  ➧ ‹@{const c}› prints a logical or syntactic constant ‹c›.
  
  ➧ ‹@{abbrev c x1 … xn}› prints a constant abbreviation ‹c x1 … xn ≡ rhs›
  as defined in the current context.

  ➧ ‹@{typ τ}› prints a well-formed type ‹τ›.

  ➧ ‹@{type κ}› prints a (logical or syntactic) type constructor ‹κ›.

  ➧ ‹@{class c}› prints a class ‹c›.

  ➧ ‹@{command name}›, ‹@{method name}›, ‹@{attribute name}› print checked
  entities of the Isar language.

  ➧ ‹@{goals}› prints the current ∗‹dynamic› goal state. This is mainly for
  support of tactic-emulation scripts within Isar. Presentation of goal states
  does not conform to the idea of human-readable proof documents!

  When explaining proofs in detail it is usually better to spell out the
  reasoning via proper Isar proof commands, instead of peeking at the internal
  machine configuration.
  
  ➧ ‹@{subgoals}› is similar to ‹@{goals}›, but does not print the main goal.
  
  ➧ ‹@{prf a1 … an}› prints the (compact) proof terms corresponding to the
  theorems ‹a1 … an›. Note that this requires proof terms to be switched on
  for the current logic session.
  
  ➧ ‹@{full_prf a1 … an}› is like ‹@{prf a1 … an}›, but prints the full
  proof terms, i.e.\ also displays information omitted in the compact proof
  term, which is denoted by ``‹_›'' placeholders there.
  
  ➧ ‹@{ML s}›, ‹@{ML_op s}›, ‹@{ML_type s}›, ‹@{ML_structure s}›, and
  ‹@{ML_functor s}› check text ‹s› as ML value, infix operator, type,
  structure, and functor respectively. The source is printed verbatim.

  ➧ ‹@{emph s}› prints document source recursively, with {\LaTeX} markup
  ▩‹\emph{›‹…›▩‹}›.

  ➧ ‹@{bold s}› prints document source recursively, with {\LaTeX} markup
  ▩‹\textbf{›‹…›▩‹}›.

  ➧ ‹@{verbatim s}› prints uninterpreted source text literally as ASCII
  characters, using some type-writer font style.

  ➧ ‹@{file path}› checks that ‹path› refers to a file (or directory) and
  prints it verbatim.

  ➧ ‹@{file_unchecked path}› is like ‹@{file path}›, but does not check the
  existence of the ‹path› within the file-system.

  ➧ ‹@{url name}› produces markup for the given URL, which results in an
  active hyperlink within the text.

  ➧ ‹@{cite name}› produces a citation ▩‹\cite{name}› in {\LaTeX}, where the
  name refers to some Bib{\TeX} database entry.

  The variant ‹@{cite ‹opt› name}› produces ▩‹\cite[opt]{name}› with some
  free-form optional argument. Multiple names are output with commas, e.g.
  ‹@{cite foo \<AND> bar}› becomes ▩‹\cite{foo,bar}›.

  The {\LaTeX} macro name is determined by the antiquotation option
  @{antiquotation_option_def cite_macro}, or the configuration option
  @{attribute cite_macro} in the context. For example, ‹@{cite [cite_macro =
  nocite] foobar}› produces ▩‹\nocite{foobar}›.

  ➧ @{command "print_antiquotations"} prints all document antiquotations that
  are defined in the current context; the ``‹!›'' option indicates extra
  verbosity.
›


subsection ‹Styled antiquotations›

text ‹
  The antiquotations ‹thm›, ‹prop› and ‹term› admit an extra ∗‹style›
  specification to modify the printed result. A style is specified by a name
  with a possibly empty number of arguments; multiple styles can be sequenced
  with commas. The following standard styles are available:

  ➧ ‹lhs› extracts the first argument of any application form with at least
  two arguments --- typically meta-level or object-level equality, or any
  other binary relation.
  
  ➧ ‹rhs› is like ‹lhs›, but extracts the second argument.
  
  ➧ ‹concl› extracts the conclusion ‹C› from a rule in Horn-clause normal form
  ‹A1 ⟹ … An ⟹ C›.
  
  ➧ ‹prem› ‹n› extract premise number ‹n› from from a rule in Horn-clause
  normal form ‹A1 ⟹ … An ⟹ C›.
›


subsection ‹General options›

text ‹
  The following options are available to tune the printed output of
  antiquotations. Note that many of these coincide with system and
  configuration options of the same names.

    ➧ @{antiquotation_option_def show_types}~‹= bool› and
    @{antiquotation_option_def show_sorts}~‹= bool› control printing of
    explicit type and sort constraints.

    ➧ @{antiquotation_option_def show_structs}~‹= bool› controls printing of
    implicit structures.

    ➧ @{antiquotation_option_def show_abbrevs}~‹= bool› controls folding of
    abbreviations.

    ➧ @{antiquotation_option_def names_long}~‹= bool› forces names of types
    and constants etc.\ to be printed in their fully qualified internal form.

    ➧ @{antiquotation_option_def names_short}~‹= bool› forces names of types
    and constants etc.\ to be printed unqualified. Note that internalizing the
    output again in the current context may well yield a different result.

    ➧ @{antiquotation_option_def names_unique}~‹= bool› determines whether the
    printed version of qualified names should be made sufficiently long to
    avoid overlap with names declared further back. Set to ‹false› for more
    concise output.

    ➧ @{antiquotation_option_def eta_contract}~‹= bool› prints terms in
    ‹η›-contracted form.

    ➧ @{antiquotation_option_def display}~‹= bool› indicates if the text is to
    be output as multi-line ``display material'', rather than a small piece of
    text without line breaks (which is the default).

    In this mode the embedded entities are printed in the same style as the
    main theory text.

    ➧ @{antiquotation_option_def break}~‹= bool› controls line breaks in
    non-display material.

    ➧ @{antiquotation_option_def quotes}~‹= bool› indicates if the output
    should be enclosed in double quotes.

    ➧ @{antiquotation_option_def mode}~‹= name› adds ‹name› to the print mode
    to be used for presentation. Note that the standard setup for {\LaTeX}
    output is already present by default, with mode ``‹latex›''.

    ➧ @{antiquotation_option_def margin}~‹= nat› and
    @{antiquotation_option_def indent}~‹= nat› change the margin or
    indentation for pretty printing of display material.

    ➧ @{antiquotation_option_def goals_limit}~‹= nat› determines the maximum
    number of subgoals to be printed (for goal-based antiquotation).

    ➧ @{antiquotation_option_def source}~‹= bool› prints the original source
    text of the antiquotation arguments, rather than its internal
    representation. Note that formal checking of @{antiquotation "thm"},
    @{antiquotation "term"}, etc. is still enabled; use the @{antiquotation
    "text"} antiquotation for unchecked output.

    Regular ‹term› and ‹typ› antiquotations with ‹source = false› involve a
    full round-trip from the original source to an internalized logical entity
    back to a source form, according to the syntax of the current context.
    Thus the printed output is not under direct control of the author, it may
    even fluctuate a bit as the underlying theory is changed later on.

    In contrast, @{antiquotation_option source}~‹= true› admits direct
    printing of the given source text, with the desirable well-formedness
    check in the background, but without modification of the printed text.

  For Boolean flags, ``‹name = true›'' may be abbreviated as ``‹name›''. All
  of the above flags are disabled by default, unless changed specifically for
  a logic session in the corresponding ▩‹ROOT› file.
›


section ‹Markdown-like text structure›

text ‹
  The markup commands @{command_ref text}, @{command_ref txt}, @{command_ref
  text_raw} (\secref{sec:markup}) consist of plain text. Its internal
  structure consists of paragraphs and (nested) lists, using special Isabelle
  symbols and some rules for indentation and blank lines. This quasi-visual
  format resembles ∗‹Markdown›⁋‹@{url "http://commonmark.org"}›, but the
  full complexity of that notation is avoided.

  This is a summary of the main principles of minimal Markdown in Isabelle:

    ▪ List items start with the following markers
      ➧[itemize:] ▩‹▪›
      ➧[enumerate:] ▩‹▸›
      ➧[description:] ▩‹➧›

    ▪ Adjacent list items with same indentation and same marker are grouped
    into a single list.

    ▪ Singleton blank lines separate paragraphs.

    ▪ Multiple blank lines escape from the current list hierarchy.

  Notable differences to official Markdown:

    ▪ Indentation of list items needs to match exactly.

    ▪ Indentation is unlimited (official Markdown interprets four spaces as
    block quote).

    ▪ List items always consist of paragraphs --- there is no notion of
    ``tight'' list.

    ▪ Section headings are expressed via Isar document markup commands
    (\secref{sec:markup}).

    ▪ URLs, font styles, other special content is expressed via antiquotations
    (\secref{sec:antiq}), usually with proper nesting of sub-languages via
    text cartouches.
›


section ‹Markup via command tags \label{sec:tags}›

text ‹
  Each Isabelle/Isar command may be decorated by additional presentation tags,
  to indicate some modification in the way it is printed in the document.

  @{rail ‹
    @{syntax_def tags}: ( tag * )
    ;
    tag: '%' (@{syntax ident} | @{syntax string})
  ›}

  Some tags are pre-declared for certain classes of commands, serving as
  default markup if no tags are given in the text:

  ┉
  \begin{tabular}{ll}
    ‹theory› & theory begin/end \\
    ‹proof› & all proof commands \\
    ‹ML› & all commands involving ML code \\
  \end{tabular}
  ┉

  The Isabelle document preparation system @{cite "isabelle-system"} allows
  tagged command regions to be presented specifically, e.g.\ to fold proof
  texts, or drop parts of the text completely.

  For example ``@{command "by"}~‹%invisible auto›'' causes that piece of proof
  to be treated as ‹invisible› instead of ‹proof› (the default), which may be
  shown or hidden depending on the document setup. In contrast, ``@{command
  "by"}~‹%visible auto›'' forces this text to be shown invariably.

  Explicit tag specifications within a proof apply to all subsequent commands
  of the same level of nesting. For example, ``@{command "proof"}~‹%visible
  …›~@{command "qed"}'' forces the whole sub-proof to be typeset as ‹visible›
  (unless some of its parts are tagged differently).

  ┉
  Command tags merely produce certain markup environments for type-setting.
  The meaning of these is determined by {\LaTeX} macros, as defined in @{file
  "~~/lib/texinputs/isabelle.sty"} or by the document author. The Isabelle
  document preparation tools also provide some high-level options to specify
  the meaning of arbitrary tags to ``keep'', ``drop'', or ``fold'' the
  corresponding parts of the text. Logic sessions may also specify ``document
  versions'', where given tags are interpreted in some particular way. Again
  see @{cite "isabelle-system"} for further details.
›


section ‹Railroad diagrams›

text ‹
  \begin{matharray}{rcl}
    @{antiquotation_def "rail"} & : & ‹antiquotation› \\
  \end{matharray}

  @{rail ‹
    'rail' @{syntax text}
  ›}

  The @{antiquotation rail} antiquotation allows to include syntax diagrams
  into Isabelle documents. {\LaTeX} requires the style file @{file
  "~~/lib/texinputs/railsetup.sty"}, which can be used via
  ▩‹\usepackage{railsetup}› in ▩‹root.tex›, for example.

  The rail specification language is quoted here as Isabelle @{syntax string}
  or text @{syntax "cartouche"}; it has its own grammar given below.

  \begingroup
  \def\isasymnewline{\isatt{\isacharbackslash\isacharless newline\isachargreater}}
  @{rail ‹
  rule? + ';'
  ;
  rule: ((identifier | @{syntax antiquotation}) ':')? body
  ;
  body: concatenation + '|'
  ;
  concatenation: ((atom '?'?) +) (('*' | '+') atom?)?
  ;
  atom: '(' body? ')' | identifier |
    '@'? (string | @{syntax antiquotation}) |
    '⏎'
  ›}
  \endgroup

  The lexical syntax of ‹identifier› coincides with that of @{syntax ident} in
  regular Isabelle syntax, but ‹string› uses single quotes instead of double
  quotes of the standard @{syntax string} category.

  Each ‹rule› defines a formal language (with optional name), using a notation
  that is similar to EBNF or regular expressions with recursion. The meaning
  and visual appearance of these rail language elements is illustrated by the
  following representative examples.

  ▪ Empty ▩‹()›

  @{rail ‹()›}

  ▪ Nonterminal ▩‹A›

  @{rail ‹A›}

  ▪ Nonterminal via Isabelle antiquotation ▩‹@{syntax method}›

  @{rail ‹@{syntax method}›}

  ▪ Terminal ▩‹'xyz'›

  @{rail ‹'xyz'›}

  ▪ Terminal in keyword style ▩‹@'xyz'›

  @{rail ‹@'xyz'›}

  ▪ Terminal via Isabelle antiquotation ▩‹@@{method rule}›

  @{rail ‹@@{method rule}›}

  ▪ Concatenation ▩‹A B C›

  @{rail ‹A B C›}

  ▪ Newline inside concatenation ▩‹A B C ⏎ D E F›

  @{rail ‹A B C ⏎ D E F›}

  ▪ Variants ▩‹A | B | C›

  @{rail ‹A | B | C›}

  ▪ Option ▩‹A ?›

  @{rail ‹A ?›}

  ▪ Repetition ▩‹A *›

  @{rail ‹A *›}

  ▪ Repetition with separator ▩‹A * sep›

  @{rail ‹A * sep›}

  ▪ Strict repetition ▩‹A +›

  @{rail ‹A +›}

  ▪ Strict repetition with separator ▩‹A + sep›

  @{rail ‹A + sep›}
›


section ‹Draft presentation›

text ‹
  \begin{matharray}{rcl}
    @{command_def "display_drafts"}‹*› & : & ‹any →› \\
  \end{matharray}

  @{rail ‹
    @@{command display_drafts} (@{syntax name} +)
  ›}

  ➧ @{command "display_drafts"}~‹paths› performs simple output of a given list
  of raw source files. Only those symbols that do not require additional
  {\LaTeX} packages are displayed properly, everything else is left verbatim.
›

end