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5 The Converters and an XML Parser
5.1 Producing Documentation from Source Files
5.1-1 MakeGAPDocDoc
5.2 Parsing XML Documents
5.2-1 ParseTreeXMLString
5.2-2 StringXMLElement
5.2-3 EntitySubstitution
5.2-4 DisplayXMLStructure
5.2-5 ApplyToNodesParseTree
5.2-6 GetTextXMLTree
5.2-7 XMLElements
5.2-8 CheckAndCleanGapDocTree
5.2-9 AddParagraphNumbersGapDocTree
5.2-10 InfoXMLParser
5.2-11 XMLValidate
5.2-12 ValidateGAPDoc
5.3 The Converters
5.3-1 GAPDoc2LaTeX
5.3-2 GAPDoc2Text
5.3-3 GAPDoc2TextPrintTextFiles
5.3-4 AddPageNumbersToSix
5.3-5 PrintSixFile
5.3-6 SetGAPDocTextTheme
5.3-7 GAPDoc2HTML
5.3-8 GAPDoc2HTMLPrintHTMLFiles
5.3-9 Stylesheet files
5.3-10 CopyHTMLStyleFiles
5.3-11 SetGAPDocHTMLStyle
5.3-12 InfoGAPDoc
5.3-13 SetGapDocLanguage
5.4 Testing Manual Examples
5.4-1 ExtractExamples
5.4-2 RunExamples

### 5 The Converters and an XML Parser

The GAPDoc package contains a set of programs which allow us to convert a GAPDoc book into several output versions and to make them available to GAP's online help.

Currently the following output formats are provided: text for browsing inside a terminal running GAP, LaTeX with `hyperref`-package for cross references via hyperlinks and HTML for reading with a Web-browser.

#### 5.1 Producing Documentation from Source Files

Here we explain how to use the functions which are described in more detail in the following sections. We assume that we have the main file `MyBook.xml` of a book `"MyBook"` in the directory `/my/book/path`. This contains `<#Include ...>`-statements as explained in Chapter 4. These refer to some other files as well as pieces of text which are found in the comments of some GAP source files `../lib/a.gd` and `../lib/b.gi` (relative to the path above). A BibTeX database `MyBook.bib` for the citations is also in the directory given above. We want to produce a text-, `pdf-` and HTML-version of the document. (A LaTeX version of the manual is produced, so it is also easy to compile `dvi`-, and postscript-versions.)

All the commands shown in this Section are collected in the single function `MakeGAPDocDoc` (5.1-1).

First we construct the complete XML-document as a string with `ComposedDocument` (4.2-1). This interprets recursively the `<#Include ...>`-statements.

    gap> path := Directory("/my/book/path");;
    gap> main := "MyBook.xml";;
    gap> files := ["../lib/a.gd", "../lib/b.gi"];;
    gap> bookname := "MyBook";;
    gap> doc := ComposedDocument("GAPDoc", path, main, files, true);;

Now `doc` is a list with two entries, the first is a string containing the XML-document, the second gives information from which files and locations which part of the document was collected. This is useful in the next step, if there are any errors in the document.

Next we parse the document and store its structure in a tree-like data structure. The commands for this are `ParseTreeXMLString` (5.2-1) and `CheckAndCleanGapDocTree` (5.2-8).

    gap> r := ParseTreeXMLString(doc[1], doc[2]);;
    gap> CheckAndCleanGapDocTree(r);
    true

We start to produce a text version of the manual, which can be read in a terminal (window). The command is `GAPDoc2Text` (5.3-2). This produces a record with the actual text and some additional information. The text can be written chapter-wise into files with `GAPDoc2TextPrintTextFiles` (5.3-3). The names of these files are `chap0.txt`, `chap1.txt` and so on. The text contains some markup using ANSI escape sequences. This markup is substituted by the GAP help system (user configurable) to show the text with colors and other attributes. For the bibliography we have to tell `GAPDoc2Text` (5.3-2) the location of the BibTeX database by specifying a `path` as second argument.

    gap> t := GAPDoc2Text(r, path);;
    gap> GAPDoc2TextPrintTextFiles(t, path);

This command constructs all parts of the document including table of contents, bibliography and index. The functions `FormatParagraph` (6.1-4) for formatting text paragraphs and `ParseBibFiles` (7.1-1) for reading BibTeX files with GAP may be of independent interest.

With the text version we have also produced the information which is used for searching with GAP's online help. Also, labels are produced which can be used by links in the HTML- and `pdf`-versions of the manual.

Next we produce a LaTeX version of the document. `GAPDoc2LaTeX` (5.3-1) returns a string containing the LaTeX source. The utility function `FileString` (6.3-5) writes the content of a string to a file, we choose `MyBook.tex`.

    gap> l := GAPDoc2LaTeX(r);;
    gap> FileString(Filename(path, Concatenation(bookname, ".tex")), l);

Assuming that you have a sufficiently good installation of TeX available (see `GAPDoc2LaTeX` (5.3-1) for details) this can be processed with a series of commands like in the following example.

    cd /my/book/path
    pdflatex MyBook
    bibtex MyBook
    pdflatex MyBook
    makeindex MyBook
    pdflatex MyBook
    mv MyBook.pdf manual.pdf

After this we have a `pdf`-version of the document in the file `manual.pdf`. It contains hyperlink information which can be used with appropriate browsers for convenient reading of the document on screen (e.g., `xpdf` is nice because it allows remote calls to display named locations of the document). Of course, we could also use other commands like `latex` or `dvips` to process the LaTeX source file. Furthermore we have produced a file `MyBook.pnr` which is GAP-readable and contains the page number information for each (sub-)section of the document.

We can add this page number information to the indexing information collected by the text converter and then print a `manual.six` file which is read by GAP when the manual is loaded. This is done with `AddPageNumbersToSix` (5.3-4) and `PrintSixFile` (5.3-5).

    gap> AddPageNumbersToSix(r, Filename(path, "MyBook.pnr"));
    gap> PrintSixFile(Filename(path, "manual.six"), r, bookname);

Finally we produce an HTML-version of the document and write it (chapter-wise) into files `chap0.html`, `chap1.html` and so on. They can be read with any Web-browser. The commands are `GAPDoc2HTML` (5.3-7) and `GAPDoc2HTMLPrintHTMLFiles` (5.3-8). We also add a link from `manual.html` to `chap0.html`. You probably want to copy stylesheet files into the same directory, see 5.3-9 for more details. The argument `path` of `GAPDoc2HTML` (5.3-7) specifies the directory containing the BibTeX database files.

    gap> h := GAPDoc2HTML(r, path);;
    gap> GAPDoc2HTMLPrintHTMLFiles(h, path);

##### 5.1-1 MakeGAPDocDoc

`‣ MakeGAPDocDoc`( path, main, files, bookname[, gaproot][, ...] ) | ( function )

This function collects all the commands for producing a text-, `pdf`- and HTML-version of a GAPDoc document as described in Section 5.1. It checks the `.log` file from the call of `pdflatex` and reports if there are errors, warnings or overfull boxes.

Note: If this function works for you depends on your operating system and installed software. It will probably work on most `UNIX` systems with a standard LaTeX installation. If the function doesn't work for you look at the source code and adjust it to your system.

Here path must be the directory (as string or directory object) containing the main file main of the document (given with or without the `.xml` extension. The argument files is a list of (probably source code) files relative to path which contain pieces of documentation which must be included in the document, see Chapter 4. And bookname is the name of the book used by GAP's online help. The optional argument gaproot must be a string which gives the relative path from path to the main GAP root directory. If this is given, the HTML files are produced with relative paths to external books.

If the string `"nopdf"` is given as optional argument then `MakeGAPDocDoc` will not produce a `pdf`-version of the help book (the source `.tex`-file is generated). Consequently, the index for the help system will not contain page numbers for the `pdf`-version. This variant of `MakeGAPDocDoc` should work independently of the operating system because no external programs are called. It is recommended that distributed manuals contain the `pdf`-version.

`MakeGAPDocDoc` can be called with additional arguments `"MathJax"`, `"Tth"` and/or `"MathML"`. If these are given additional variants of the HTML conversion are called, see `GAPDoc2HTML` (5.3-7) for details.

It is possible to use GAPDoc with other languages than English, see `SetGapDocLanguage` (5.3-13) for more details.

#### 5.2 Parsing XML Documents

Arbitrary well-formed XML documents can be parsed and browsed by the following functions. A proper validation can be done with an external program, see `XMLValidate` (5.2-11) below.

##### 5.2-1 ParseTreeXMLString

`‣ ParseTreeXMLString`( str[, srcinfo][, entitydict] ) | ( function )

`‣ ParseTreeXMLFile`( fname[, entitydict] ) | ( function )

Returns: a record which is root of a tree structure

The first function parses an XML-document stored in string str and returns the document in form of a tree.

The optional argument srcinfo must have the same format as in `OriginalPositionDocument` (4.2-2). If it is given then error messages refer to the original source of the text with the problem.

With the optional argument entitydict named entities can be given to the parser, for example entities which are defined in the `.dtd`-file (which is not read by this parser). The standard XML-entities do not need to be provided, and for GAPDoc documents the entity definitions from `gapdoc.dtd` are automatically provided. Entities in the document's `<!DOCTYPE` declaration are parsed and also need not to be provided here. The argument entitydict must be a record where each component name is an entity name (without the surrounding & and ;) to which is assigned its substitution string.

The second function is just a shortcut for `ParseTreeXMLString( StringFile(`fname`), ... )`, see `StringFile` (6.3-5).

After these functions return the list of named entities which were known during the parsing can be found in the record `ENTITYDICT`.

A node in the result tree corresponds to an XML element, or to some parsed character data. In the first case it looks as follows:

    rec( name := "Book",
         attributes := rec( Name := "EDIM" ),
         content := [ ... list of nodes for content ...],
         start := 312,
         stop := 15610,
         next := 15611     )

This means that `str{[312..15610]}` looks like `<Book Name="EDIM"> ... content ... </Book>`.

The leaves of the tree encode parsed character data as in the following example:

    rec( name := "PCDATA",
         content := "text without markup "     )

This function checks whether the XML document is well formed, see 2.1-14 for an explanation. If an error in the XML structure is found, a break loop is entered and the text around the position where the problem starts is shown. With `Show();` one can browse the original input in the `Pager` (Reference: Pager), starting with the line where the error occurred. All entities are resolved when they are either entities defined in the GAPDoc package (in particular the standard XML entities) or if their definition is included in the `<!DOCTYPE ..>` tag of the document.

Note that `ParseTreeXMLString` does not parse and interpret the corresponding document type definition (the `.dtd`-file given in the `<!DOCTYPE ..>` tag). Hence it also does not check the validity of the document (i.e., it is no validating XML parser).

If you are using this function to parse a GAPDoc document you can use `CheckAndCleanGapDocTree` (5.2-8) for some validation and additional checking of the document structure.

##### 5.2-2 StringXMLElement

`‣ StringXMLElement`( tree ) | ( function )

Returns: a list `[string, positions]`

The argument tree must have a format of a node in the parse tree of an XML document as returned by `ParseTreeXMLString` (5.2-1) (including the root node representing the full document). This function computes a pair `[string, positions]` where `string` contains XML code which is equivalent to the code which was parsed to get tree. And `positions` is a list of lists of four numbers `[eltb, elte, contb, conte]`. There is one such list for each XML element occuring in `string`, where `eltb` and `elte` are the begin and end position of this element in `string` and where `contb` and `conte` are begin and end position of the content of this element, or both are `0` if there is no content.

Note that parsing XML code is an irreversible task, we can only expect to get equivalent XML code from this function. But parsing the resulting `string` again and applying `StringXMLElement` again gives the same result. See the function `EntitySubstitution` (5.2-3) for back-substitutions of entities in the result.

##### 5.2-3 EntitySubstitution

`‣ EntitySubstitution`( xmlstring, entities ) | ( function )

Returns: a string

The argument xmlstring must be a string containing XML code or a pair `[string, positions]` as returned by `StringXMLElement` (5.2-2). The argument entities specifies entity names (without the surrounding & and `;`) and their substitution strings, either a list of pairs of strings or as a record with the names as components and the substitutions as values.

This function tries to substitute non-intersecting parts of `string` by the given entities. If the `positions` information is given then only parts of the document which allow a valid substitution by an entity are considered. Otherwise a simple text substitution without further check is done.

Note that in general the entity resolution in XML documents is a complicated and non-reversible task. But nevertheless this utility may be useful in not too complicated situations.

##### 5.2-4 DisplayXMLStructure

`‣ DisplayXMLStructure`( tree ) | ( function )

This utility displays the tree structure of an XML document as it is returned by `ParseTreeXMLString` (5.2-1) (without the `PCDATA` leaves).

Since this is usually quite long the result is shown using the `Pager` (Reference: Pager).

##### 5.2-5 ApplyToNodesParseTree

`‣ ApplyToNodesParseTree`( tree, fun ) | ( function )

`‣ AddRootParseTree`( tree ) | ( function )

`‣ RemoveRootParseTree`( tree ) | ( function )

The function `ApplyToNodesParseTree` applies a function fun to all nodes of the parse tree tree of an XML document returned by `ParseTreeXMLString` (5.2-1).

The function `AddRootParseTree` is an application of this. It adds to all nodes a component `.root` to which the top node tree tree is assigned. These components can be removed afterwards with `RemoveRootParseTree`.

Here are two more utilities which use `ApplyToNodesParseTree`.

##### 5.2-6 GetTextXMLTree

`‣ GetTextXMLTree`( tree ) | ( function )

Returns: a string

The argument tree must be a node of a parse tree of some XML document, see `ParseTreeXMLFile` (5.2-1). This function collects the content of this and all included elements recursively into a string.

##### 5.2-7 XMLElements

`‣ XMLElements`( tree, eltnames ) | ( function )

Returns: a list of nodes

The argument tree must be a node of a parse tree of some XML document, see `ParseTreeXMLFile` (5.2-1). This function returns a list of all subnodes of tree (possibly including tree) of elements with name given in the list of strings eltnames. Use `"PCDATA"` as name for leave nodes which contain the actual text of the document. As an abbreviation eltnames can also be a string which is then put in a one element list.

And here are utilities for processing GAPDoc XML documents.

##### 5.2-8 CheckAndCleanGapDocTree

`‣ CheckAndCleanGapDocTree`( tree ) | ( function )

Returns: nothing

The argument tree of this function is a parse tree from `ParseTreeXMLString` (5.2-1) of some GAPDoc document. This function does an (incomplete) validity check of the document according to the document type declaration in `gapdoc.dtd`. It also does some additional checks which cannot be described in the DTD (like checking whether chapters and sections have a heading). For elements with element content the whitespace between these elements is removed.

In case of an error the break loop is entered and the position of the error in the original XML document is printed. With `Show();` one can browse the original input in the `Pager` (Reference: Pager).

##### 5.2-9 AddParagraphNumbersGapDocTree

`‣ AddParagraphNumbersGapDocTree`( tree ) | ( function )

Returns: nothing

The argument tree must be an XML tree returned by `ParseTreeXMLString` (5.2-1) applied to a GAPDoc document. This function adds to each node of the tree a component `.count` which is of form `[Chapter[, Section[, Subsection, Paragraph] ] ]`. Here the first three numbers should be the same as produced by the LaTeX version of the document. Text before the first chapter is counted as chapter `0` and similarly for sections and subsections. Some elements are always considered to start a new paragraph.

##### 5.2-10 InfoXMLParser

`‣ InfoXMLParser` | ( info class )

The default level of this info class is 1. Functions like `ParseTreeXMLString` (5.2-1) are then printing some information, in particular in case of errors. You can suppress it by setting the level of `InfoXMLParser` to 0. With level 2 there may be some more information for debugging purposes. Messages with warnings (indicating that something should be fixed) start with the string `#W` (this can be used in automatized tests).

##### 5.2-11 XMLValidate

`‣ XMLValidate`( doc, dtdpath ) | ( function )

Returns: `fail` or a record

The argument doc must be a string which is an XML document, and dtdpath is a path containing the corresponding DTD file.

The function returns `fail` if the program `xmllint` cannot be called.

Otherwise the document is validated via the external program `xmllint` via the function `IO_PipeThroughWithError` (IO: IO_PipeThroughWithError), and its resulting record is returned.

##### 5.2-12 ValidateGAPDoc

`‣ ValidateGAPDoc`( doc ) | ( function )

Returns: `fail`, `true` or a record

The argument doc must be a string which is a GAPDoc XML document or a pair of a string and list as returned by `ComposedDocument` (4.2-1) with argument info set to `true`.

The function returns `fail` in case of a problem.

Otherwise the document is validated using `XMLValidate` (5.2-11). If the validation was successful this function returns `true`. In the case of validation errors some information is printed and the result of `XMLValidate` (5.2-11) is returned.

    gap> fn := Filename(DirectoriesPackageLibrary("gapdoc", ""),
    >                                             "3k+1/3k+1.xml");;
    gap> doc := ComposedDocument("GAPDoc", "", fn, [], true);;
    gap> doc[1][220] := 't';;
    gap> check := ValidateGAPDoc(doc);;
    ValidateGAPDoc found problems:
    Line 11:  parser error : Opening and ending tag mismatch
       source position: /opt/gap/pkg/GAPDoc-1.6.4/3k+1/3k+1.xml, line 11

#### 5.3 The Converters

Here are more details about the conversion programs for GAPDoc XML documents.

##### 5.3-1 GAPDoc2LaTeX

`‣ GAPDoc2LaTeX`( tree ) | ( function )

Returns: LaTeX document as string

`‣ SetGapDocLaTeXOptions`( [...] ) | ( function )

Returns: Nothing

The argument tree for this function is a tree describing a GAPDoc XML document as returned by `ParseTreeXMLString` (5.2-1) (probably also checked with `CheckAndCleanGapDocTree` (5.2-8)). The output is a string containing a version of the document which can be written to a file and processed with LaTeX or pdfLaTeX (and probably BibTeX and `makeindex`).

The output uses the `report` document class and needs the following LaTeX packages: `amssymb`, `inputenc`, `makeidx`, `color`, `fancyvrb`, `psnfss`, `pslatex`, `enumitem` and `hyperref`. These are for example provided by the texlive distribution of TeX (which in turn is used for most TeX packages of current Linux distributions); see https://www.tug.org/texlive/.

In particular, the resulting `pdf`-output (and `dvi`-output) contains (internal and external) hyperlinks which can be very useful for onscreen browsing of the document.

The LaTeX processing also produces a file with extension `.pnr` which is GAP readable and contains the page numbers for all (sub)sections of the document. This can be used by GAP's online help; see `AddPageNumbersToSix` (5.3-4). Non-ASCII characters in the GAPDoc document are translated to LaTeX input in ASCII-encoding with the help of `Encode` (6.2-2) and the option `"LaTeX"`. See the documentation of `Encode` (6.2-2) for how to proceed if you have a character which is not handled (yet).

This function works by running recursively through the document tree and calling a handler function for each GAPDoc XML element. Many of these handler functions (usually in `GAPDoc2LaTeXProcs.<ElementName>`) are not difficult to understand (the greatest complications are some commands for index entries, labels or the output of page number information). So it should be easy to adjust layout details to your own taste by slight modifications of the program.

Former versions of GAPDoc supported some XML processing instructions to add some extra lines to the preamble of the LaTeX document. Its use is now deprecated, use the much more flexible `SetGapDocLaTeXOptions` instead: The default layout of the resulting documents can be changed with `SetGapDocLaTeXOptions`. This changes parts of the header of the LaTeX file produced by GAPDoc. You can see the header with some placeholders by `Page(GAPDoc2LaTeXProcs.Head);`. The placeholders are filled with components from the record `GAPDoc2LaTeXProcs.DefaultOptions`. The arguments of `SetGapDocLaTeXOptions` can be records with the same structure (or parts of it) with different values. As abbreviations there are also three strings supported as arguments. These are `"nocolor"` for switching all colors to black; then `"nopslatex"` to use standard LaTeX fonts instead of postscript fonts; and finally `"utf8"` to choose UTF-8 as input encoding for the LaTeX document.

##### 5.3-2 GAPDoc2Text

`‣ GAPDoc2Text`( tree[, bibpath][, width] ) | ( function )

Returns: record containing text files as strings and other information

The argument tree for this function is a tree describing a GAPDoc XML document as returned by `ParseTreeXMLString` (5.2-1) (probably also checked with `CheckAndCleanGapDocTree` (5.2-8)). This function produces a text version of the document which can be used with GAP's online help (with the `"screen"` viewer, see `SetHelpViewer` (Reference: SetHelpViewer)). It includes title page, bibliography and index. The bibliography is made from BibXMLext or BibTeX databases, see 7. Their location must be given with the argument bibpath (as string or directory object).

The output is a record with one component for each chapter (with names `"0"`, `"1"`, ..., `"Bib"` and `"Ind"`). Each such component is again a record with the following components:

`text`

  the text of the whole chapter as a string

`ssnr`

  list of subsection numbers in this chapter (like `[3, 2, 1]` for chapter 3, section 2, subsection 1)

`linenr`

  corresponding list of line numbers where the subsections start

`len`

  number of lines of this chapter

The result can be written into files with the command `GAPDoc2TextPrintTextFiles` (5.3-3).

As a side effect this function also produces the `manual.six` information which is used for searching in GAP's online help. This is stored in `tree.six` and can be printed into a `manual.six` file with `PrintSixFile` (5.3-5) (preferably after producing a LaTeX version of the document as well and adding the page number information to `tree.six`, see `GAPDoc2LaTeX` (5.3-1) and `AddPageNumbersToSix` (5.3-4)).

The text produced by this function contains some markup via ANSI escape sequences. The sequences used here are usually ignored by terminals. But the GAP help system will substitute them by interpreted color and attribute sequences (see `TextAttr` (6.1-2)) before displaying them. There is a default markup used for this but it can also be configured by the user, see `SetGAPDocTextTheme` (5.3-6). Furthermore, the text produced is in UTF-8 encoding. The encoding is also translated on the fly, if `GAPInfo.TermEncoding` is set to some encoding supported by `Encode` (6.2-2), e.g., `"ISO-8859-1"` or `"latin1"`.

With the optional argument width a different length of the output text lines can be chosen. The default is 76 and all lines in the resulting text start with two spaces. This looks good on a terminal with a standard width of 80 characters and you probably don't want to use this argument.

##### 5.3-3 GAPDoc2TextPrintTextFiles

`‣ GAPDoc2TextPrintTextFiles`( t[, path] ) | ( function )

Returns: nothing

The first argument must be a result returned by `GAPDoc2Text` (5.3-2). The second argument is a path for the files to write, it can be given as string or directory object. The text of each chapter is written into a separate file with name `chap0.txt`, `chap1.txt`, ..., `chapBib.txt`, and `chapInd.txt`.

If you want to make your document accessible via the GAP online help you must put at least these files for the text version into a directory, together with the file `manual.six`, see `PrintSixFile` (5.3-5). Then specify the path to the `manual.six` file in the packages `PackageInfo.g` file, see Reference: The PackageInfo.g File.

Optionally you can add the `dvi`- and `pdf`-versions of the document which are produced with `GAPDoc2LaTeX` (5.3-1) to this directory. The files must have the names `manual.dvi` and `manual.pdf`, respectively. Also you can add the files of the HTML version produced with `GAPDoc2HTML` (5.3-7) to this directory, see `GAPDoc2HTMLPrintHTMLFiles` (5.3-8). The handler functions in GAP for this help format detect automatically which of the optional formats of a book are actually available.

##### 5.3-4 AddPageNumbersToSix

`‣ AddPageNumbersToSix`( tree, pnrfile ) | ( function )

Returns: nothing

Here tree must be the XML tree of a GAPDoc document, returned by `ParseTreeXMLString` (5.2-1). Running `latex` on the result of `GAPDoc2LaTeX(tree)` produces a file pnrfile (with extension `.pnr`). The command `GAPDoc2Text(tree)` creates a component `tree.six` which contains all information about the document for the GAP online help, except the page numbers in the `.dvi, .ps, .pdf` versions of the document. This command adds the missing page number information to `tree.six`.

##### 5.3-5 PrintSixFile

`‣ PrintSixFile`( tree, bookname, fname ) | ( function )

Returns: nothing

This function prints the `.six` file fname for a GAPDoc document stored in tree with name bookname. Such a file contains all information about the book which is needed by the GAP online help. This information must first be created by calls of `GAPDoc2Text` (5.3-2) and `AddPageNumbersToSix` (5.3-4).

##### 5.3-6 SetGAPDocTextTheme

`‣ SetGAPDocTextTheme`( [optrec1[, optrec2], ...] ) | ( function )

Returns: nothing

This utility function is for readers of the screen version of GAP manuals which are generated by the GAPDoc package. It allows to configure the color and attribute layout of the displayed text. There is a default which can be reset by calling this function without argument.

As an abbreviation the arguments optrec1 and so on can be strings for the known name of a theme. Information about valid names is shown with `SetGAPDocTextTheme("");`.

Otherwise, optrec1 and so on must be a record. Its entries overwrite the corresponding entries in the default and in previous arguments. To construct valid markup you can use `TextAttr` (6.1-2). Entries must be either pairs of strings, which are put before and after the corresponding text, or as an abbreviation it can be a single string. In the latter case, the second string is implied; if the string contains an escape sequence the second string is `TextAttr.reset`, otherwise the given string is used. The following components are recognized:

`flush`

  `"both"` for left-right justified paragraphs, and `"left"` for ragged right ones

`Heading`

  chapter and (sub-)section headings

`Func`

  function, operation, ... names

`Arg`

  argument names in descriptions

`Example`

  example code

`Package`

  package names

`Returns`

  Returns-line in descriptions

`URL`

  URLs

`Mark`

  Marks in description lists

`K`

  GAP keywords

`C`

  code or text to type

`F`

  file names

`B`

  buttons

`M`

  simplified math elements

`Math`

  normal math elements

`Display`

  displayed math elements

`Emph`

  emphasized text

`Q`

  quoted text

`Ref`

  reference text

`Prompt`

  GAP prompt in examples

`BrkPrompt`

  GAP break prompt in examples

`GAPInput`

  GAP input in examples

`reset`

  reset to default, don't change this

`BibAuthor`

  author names in bibliography

`BibTitle`

  titles in bibliography

`BibJournal`

  journal names in bibliography

`BibVolume`

  volume number in bibliography

`BibLabel`

  labels for bibliography entries

`BibReset`

  reset for bibliography, don't change

`ListBullet`

  bullet for simple lists (2 visible characters long)

`EnumMarks`

  one visible character before and after the number in enumerated lists

`DefLineMarker`

  marker before function and variable definitions (2 visible characters long)

`FillString`

  for filling in definitions and example separator lines

    gap> # use no colors for GAP examples and
    gap> # change display of headings to bold green
    gap> SetGAPDocTextTheme("noColorPrompt",
    >            rec(Heading:=Concatenation(TextAttr.bold, TextAttr.2)));

##### 5.3-7 GAPDoc2HTML

`‣ GAPDoc2HTML`( tree[, bibpath[, gaproot]][, mtrans] ) | ( function )

Returns: record containing HTML files as strings and other information

The argument tree for this function is a tree describing a GAPDoc XML document as returned by `ParseTreeXMLString` (5.2-1) (probably also checked with `CheckAndCleanGapDocTree` (5.2-8)). Without an mtrans argument this function produces an HTML version of the document which can be read with any Web-browser and also be used with GAP's online help (see `SetHelpViewer` (Reference: SetHelpViewer)). It includes title page, bibliography, and index. The bibliography is made from BibTeX databases. Their location must be given with the argument bibpath (as string or directory object, if not given the current directory is used). If the third argument gaproot is given and is a string then this string is interpreted as relative path to GAP's main root directory. Reference-URLs to external HTML-books which begin with the GAP root path are then rewritten to start with the given relative path. This makes the HTML-documentation portable provided a package is installed in some standard location below the GAP root.

The output is a record with one component for each chapter (with names `"0"`, `"1"`, ..., `"Bib"`, and `"Ind"`). Each such component is again a record with the following components:

`text`

  the text of an HTML file containing the whole chapter (as a string)

`ssnr`

  list of subsection numbers in this chapter (like `[3, 2, 1]` for chapter 3, section 2, subsection 1)

Standard output format without mtrans argument

The HTML code produced with this converter conforms to the W3C specification XHTML 1.0 strict, see https://www.w3.org/TR/xhtml1. First, this means that the HTML files are valid XML files. Secondly, the extension strict says in particular that the code doesn't contain any explicit font or color information.

Mathematical formulae are handled as in the text converter `GAPDoc2Text` (5.3-2). We don't want to assume that the browser can use symbol fonts. Some GAP users like to browse the online help with `lynx`, see `SetHelpViewer` (Reference: SetHelpViewer), which runs inside the same terminal windows as GAP.

To view the generated files in graphical browsers, stylesheet files with layout configuration should be copied into the directory with the generated HTML files, see 5.3-9.

Output format with mtrans argument

Currently, there are three variants of this converter available which handle mathematical formulae differently. They are accessed via the optional last mtrans argument.

If mtrans is set to `"MathJax"` the formulae are essentially translated as for LaTeX documents (there is no processing of `<M>` elements as decribed in 3.8-2). Inline formulae are delimited by `\(` and `\)` and displayed formulae by `\[` and `\]`. With MathJax webpages can contain nicely formatted scalable and searchable formulae. The resulting files link by default to https://www.jsdelivr.com/ to get the MathJax script and fonts. This means that they can only be used on computers with internet access. An alternative URL can be set by overwriting `GAPDoc2HTMLProcs.MathJaxURL` before building the HTML version of a manual. This way a local installation of MathJax could be used. See https://www.mathjax.org/ for more details.

The following possibilities for mtrans are still supported, but since the MathJax approach seems much better, their use is deprecated.

If the argument mtrans is set to `"Tth"` it is assumed that you have installed the LaTeX to HTML translation program `tth`. This is used to translate the contents of the `M`, `Math` and `Display` elements into HTML code. Note that the resulting code is not compliant with any standard. Formally it is XHTML 1.0 Transitional, it contains explicit font specifications and the characters of mathematical symbols are included via their position in a Symbol font. Some graphical browsers can be configured to display this in a useful manner, check the Tth homepage for more details.

This function works by running recursively through the document tree and calling a handler function for each GAPDoc XML element. Many of these handler functions (usually in `GAPDoc2TextProcs.<ElementName>`) are not difficult to understand (the greatest complications are some commands for index entries, labels or the output of page number information). So it should be easy to adjust certain details to your own taste by slight modifications of the program.

The result of this converter can be written to files with the command `GAPDoc2HTMLPrintHTMLFiles` (5.3-8).

There are two user preferences for reading the HTML manuals produced by GAPDoc. A user can choose among several style files which determine the appearance of the manual pages with `SetUserPreference("GAPDoc", "HTMLStyle", [...]);` where the list in the third argument are arguments for `SetGAPDocHTMLStyle` (5.3-11). The second preference is set by `SetUserPreference("GAPDoc", "UseMathJax", ...);` where the third argument is `true` or `false` (default). If this is set to `true`, the GAP help system displays the MathJax version of the HTML manuals.

##### 5.3-8 GAPDoc2HTMLPrintHTMLFiles

`‣ GAPDoc2HTMLPrintHTMLFiles`( t[, path] ) | ( function )

Returns: nothing

The first argument must be a result returned by `GAPDoc2HTML` (5.3-7). The second argument is a path for the files to write, it can be given as string or directory object. The text of each chapter is written into a separate file with name `chap0.html`, `chap1.html`, ..., `chapBib.html`, and `chapInd.html`.

The MathJax versions are written to files `chap0_mj.html`, ..., `chapInd_mj.html`.

The experimental version which is produced with `tth` uses different names for the files, namely `chap0_sym.html`, and so on for files which need symbol fonts.

You should also add stylesheet files to the directory with the HTML files, see 5.3-9.

##### 5.3-9 Stylesheet files

For graphical browsers the layout of the generated HTML manuals can be highly configured by cascading stylesheet (CSS) and javascript files. Such files are provided in the `styles` directory of the GAPDoc package.

We recommend that these files are copied into each manual directory (such that each of them is selfcontained). There is a utility function `CopyHTMLStyleFiles` (5.3-10) which does this. Of course, these files may be changed or new styles may be added. New styles may also be sent to the GAPDoc authors for possible inclusion in future versions.

The generated HTML files refer to the file `manual.css` which conforms to the W3C specification CSS 2.0, see https://www.w3.org/TR/REC-CSS2, and the javascript file `manual.js` (only in browsers which support CSS or javascript, respectively; but the HTML files are also readable without any of them). To add a style `mystyle` one or both of `mystyle.css` and `mystyle.js` must be provided; these can overwrite default settings and add new javascript functions. For more details see the comments in `manual.js`.

##### 5.3-10 CopyHTMLStyleFiles

`‣ CopyHTMLStyleFiles`( dir ) | ( function )

Returns: nothing

This utility function copies the `*.css` and `*.js` files from the `styles` directory of the GAPDoc package into the directory dir.

##### 5.3-11 SetGAPDocHTMLStyle

`‣ SetGAPDocHTMLStyle`( [style1[, style2], ...] ) | ( function )

Returns: nothing

This utility function is for readers of the HTML version of GAP manuals which are generated by the GAPDoc package. It allows to configure the display style of the manuals. This will only have an effect if you are using a browser that supports javascript. There is a default which can be reset by calling this function without argument.

The arguments style1 and so on must be strings. You can find out about the valid strings by following the [Style] link on top of any manual page. (Going back to the original page, its address has a setting for `GAPDocStyle` which is the list of strings, separated by commas, you want to use here.)

    gap> # show/hide subsections in tables on contents only after click,
    gap> # and don't use colors in GAP examples
    gap> SetGAPDocHTMLStyle("toggless", "nocolorprompt");

##### 5.3-12 InfoGAPDoc

`‣ InfoGAPDoc` | ( info class )

The default level of this info class is 1. The converter functions for GAPDoc documents are then printing some information. You can suppress this by setting the level of `InfoGAPDoc` to 0. With level 2 there may be some more information for debugging purposes. Most info statements in GAPDoc just give information about the progress of functions. In some cases there are proper warnings which indicate that something should be fixed. The corresponding messages start with the string `#W` (this can be used in automatized tests). In even more serious cases of errors the message starts with `#E` .

##### 5.3-13 SetGapDocLanguage

`‣ SetGapDocLanguage`( [lang] ) | ( function )

Returns: nothing

The GAPDoc converter programs sometimes produce text which is not explicit in the document, e.g., headers like Abstract, Appendix, links to Next Chapter, variable types function and so on.

With `SetGapDocLanguage` the language for these texts can be changed. The argument lang must be a string. Calling without argument or with a language name for which no translations are available is the same as using the default `"english"`.

If your language lang is not yet available, look at the record `GAPDocTexts.english` and translate all the strings to lang. Then assign this record to `GAPDocTexts.(lang)` and send it to the GAPDoc authors for inclusion in future versions of GAPDoc. (Currently, there are translations for `english`, `german`, `russian` and `ukrainian`.)

Further hints: To get strings produced by LaTeX right you will probably use the `babel` package with option lang, see `SetGapDocLaTeXOptions` (5.3-1). If lang cannot be encoded in `latin1` encoding you can consider the use of `"utf8"` with `SetGapDocLaTeXOptions` (5.3-1).

#### 5.4 Testing Manual Examples

We also provide some tools to check and adjust the examples given in `<Example>`-elements.

Former versions of GAPDoc provided functions `ManualExamples` and `TestManualExamples`. These functions are still available, but no longer documented. Their use is deprecated.

##### 5.4-1 ExtractExamples

`‣ ExtractExamples`( path, main, files, units[, withLog] ) | ( function )

Returns: a list of lists

`‣ ExtractExamplesXMLTree`( tree, units[, withLog] ) | ( function )

Returns: a list of lists

The argument tree must be a parse tree of a GAPDoc document, see `ParseTreeXMLFile` (5.2-1). The function `ExtractExamplesXMLTree` returns a data structure representing the `<Example>` elements of the document. The return value can be used with `RunExamples` (5.4-2) to check and optionally update the examples of the document.

Depending on the argument units several examples are collected in one list. Recognized values for units are `"Chapter"`, `"Section"`, `"Subsection"` or `"Single"`. The latter means that each example is in a separate list. For all other value of units just one list with all examples is returned.

The arguments path, main and files of `ExtractExamples` are the same as for `ComposedDocument` (4.2-1). This function first contructs and parses the GAPDoc document and then applies `ExtractExamplesXMLTree`.

If the optional argument withLog is given and `true` then `<Log>` elements are handled like `<Example>` elements. This allows to put examples which can only run under certain conditions, e.g., when certain external programs are available, into `<Log>` elements. (Put example code which should also not be included by this variant into `<Listing>` elements.)

##### 5.4-2 RunExamples

`‣ RunExamples`( exmpls[, optrec] ) | ( function )

Returns: `true` or `false`

The argument exmpls must be the output of a call to `ExtractExamples` (5.4-1) or `ExtractExamplesXMLTree` (5.4-1). The optional argument optrec must be a record, its components can change the default behaviour of this function.

By default this function runs the GAP input of all examples and compares the actual output with the output given in the examples. If differences occur these are displayed together with information on the location of the source code of that example. Before running the examples in each unit (entry of exmpls) the function `START_TEST` (Reference: START_TEST) is called and the screen width is set to 72 characters.

This function returns `true` if no differences are found and `false` otherwise.

If the argument optrec is given, the following components are recognized:

`showDiffs`

  The default value is `true`, if set to something else found differences in the examples are not displayed.

`width`

  The value must be a positive integer which is used as screen width when running the examples. As mentioned above, the default is 72 which is a sensible value for the text version of the GAPDoc document used in a 80 character wide terminal.

`ignoreComments`

  The default is `false`.
  If set to `true` comments in the input will be ignored (as in the default behaviour of the `Test` (Reference: Test) function).

`changeSources`

  If this is set to `true` then the source code of all manual examples which show differences is adjusted to the current outputs. The default is `false`.
  Use this feature with care. Note that sometimes differences can indicate a bug, and in such a case it is more appropriate to fix the bug instead of changing the example output.

`compareFunction`

  The function used to compare the output shown in the example and the current output. See `Test` (Reference: Test) for more details.

`checkWidth`

  If this option is a positive integer `n` the function prints warnings if an example contains any line with more than `n` characters (input and output lines are considered). By default this option is set to `false`.

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