vtable ¶

1 序と入門 ¶

Emacsで表データを表示するほとんどのモードでtabulated-list-modeが使われていますが、制約があります。 それはテキストが等幅で表示されるということで、フォントと画像を単一のリストに混在させることが難しくなっています。 vtable（「可変ピッチ表」；variable pitch tables）パッケージはこの点に取り組んでいます。

tabulated-list-modeは主モードであって、バッファ全体を制御することが前提です。 vtableはそうではありません。 他のデータの途中にvtableがあっても、同じバッファに複数のvtableがあってもいいのです。

以下はvtableで作れる一番単純なものです。

(make-vtable
 :objects '(("Foo" 1034)
            ("Gazonk" 45)))

既定では、vtableはvtableフェイスを使います（これはvariable-pitchフェイスを継承します）。 また、数値データのみの列は右揃えにします（それ以外は左揃え）。

普通は、列に名前を付けたいでしょう。

(make-vtable
 :columns '("Name" "ID")
 :objects '(("Foo" 1034)
            ("Gazonk" 45)))

列名をクリックすると各列（この例ではリスト中の要素に対応）のデータに基づいて表を整列します。

既定では、データは「ありのままに」表示されます。 つまり、‘(format "%s" ...)’で表示されるような感じです。 ただし上塗りはできます。

(make-vtable
 :columns '("Name" "ID")
 :objects '(("Foo" 1034)
            ("Gazonk" 45))
 :formatter (lambda (value column &rest _)
              (if (= column 1)
                  (file-size-human-readable value)
                value)))

この場合、‘1034’は‘1k’と表示されます。 ただし、整列では‘45’の後にきます。 なぜなら、表示されているデータではなく、実際のデータに基づいて整列されるからです。

代えて、表の汎用の書式器ではなく、列の定義に書式器を付けられます。

(make-vtable
 :columns '("Name"
            (:name "ID" :formatter file-size-human-readable))
 :objects '(("Foo" 1034)
            ("Gazonk" 45)))

データは単純なリストでなくても構いません。 vtableにはどんな種類のオブジェクトも与えられます。 ただし、各列のデータを返す関数も書かなければなりません。 一例を上げると、以下はM-x list-buffersのとても単純なバージョンです。

(make-vtable
 :columns '("Name" "Size" "File")
 :objects (buffer-list)
 :actions '("k" kill-buffer
            "RET" display-buffer)
 :getter (lambda (object column vtable)
           (pcase (vtable-column vtable column)
             ("Name" (buffer-name object))
             ("Size" (buffer-size object))
             ("File" (or (buffer-file-name object) "")))))

この場合のobjectsはバッファのリストです。 データを表示するために、vtableはgetter関数を呼びます。 この関数は各オブジェクトの各列に呼ばれ、最終的に表示されるデータを返します。

actionsにも注意してください。 これは地点があるオブジェクトで呼ばれる単純な命令です。 そのためその行でRETと打つと、display-bufferがバッファオブジェクトを引数として呼ばれます（使うキーマップを与えることもできます。 ただしそうすると、そのオブジェクトに行き着くためのvtable-current-objectを呼ぶ命令を書かなければなりません）。

なお動作はバッファに表示されるデータには呼ばれません。 元のオブジェクトで呼ばれます。

最後に、以下は全ての機能を使うだけの例です。

(make-vtable
 :columns `(( :name "Thumb" :width "500px"
              :displayer
              ,(lambda (value max-width table)
                 (propertize "*" 'display
                             (create-image value nil nil
                                           :max-width max-width))))
            (:name "Size" :width 10
                   :formatter file-size-human-readable)
            (:name "Time" :width 10 :primary ascend)
            "Name")
 :objects-function (lambda ()
                     (directory-files "/tmp/" t "\\.jpg\\'"))
 :actions '("RET" find-file)
 :getter (lambda (object column table)
           (pcase (vtable-column table column)
             ("Name" (file-name-nondirectory object))
             ("Thumb" object)
             ("Size" (file-attribute-size (file-attributes object)))
             ("Time" (format-time-string
                      "%F" (file-attribute-modification-time
                            (file-attributes object))))))
 :separator-width 5
 :keymap (define-keymap
           "q" #'kill-buffer))

このvtableでは単純な画像閲覧器を実装しています。 （列の幅によって動的に大きさが変わる）画像サムネイル、人間にとって読みやすいファイルの大きさ、日付、ファイル名が表示されます。 区切り幅は5つの通常文字幅です。 行でRETを打つと画像を新しい窓で開きます。 qを打つとバッファを殺します。

2 概念 ¶

vtableはオブジェクトの数のデータだけ一覧にします。 各オブジェクトはリストやベクタにできますが、他のものでもできます。

特定の列の値を得るには、取得子関数がオブジェクトに呼ばれます。 取得関数が定義されていなければ、既定でオブジェクトを系列として添字で引こうとします。 何れにせよ、値が得られたら、それが整列に使われます。

この値は書式器関数で書式化されます。 この関数は値を引数に呼ばれます。 書式器はよく、値をより読み手にとって親しみやすいものにします。

最後に、書式化された値は表示器関数に渡されます。 この関数は表のフェイスを書式化された値に付けるはたらきをします。 また、列の幅より広くないようにもします。 表示器はよく、長過ぎる文字列を切り詰め、画像の大きさを拡縮します。

これら3つの変換全て、つまり取得子、書式器、表示器の関数は、列毎に定義できます。 また、表毎にもできます（列毎の変換は表毎の変換に優先します）。

表に定義される利用者の命令は表示されるデータには及びません。 引数としては元のオブジェクトで呼ばれます。

3 作表 ¶

作成のためのインターフェース関数はmake-vtableです（バッファに表を挿入できます）。 表オブジェクトを返します。

キーワード引数は以下に記述される通りです。

make-vtableでは沢山のコールバックインターフェース関数が使えます。 その多くがオブジェクト引数（:objectsリストにあるオブジェクト）、列の添字の引数（ゼロ始まり）、表の引数（make-vtableが返すオブジェクト）を取ります。

:objects

表示されるオブジェクトのリストです。 文字列のリスト（単一列の表として表示されます）か、各要素が系列であるリストです。 後者の要素は、「単純に」表示できる、文字列、数値、その他のオブジェクトの混合です。

後者の場合、:columnsがnilでなく、:columnsにあるよりも多く系列に要素があるときは、:columnsの最初の要素のみが表示されます。

:objecctsリストが空であり（かつ:objects-functionが定義されていなければ）、空のvtableが作られます。 この場合、:columnsによる仕様が提供されていなければなりません。

:objects-function

オブジェクトを動的に生成すると便利なことはよくあります（例えば作業内容を自動で復元するなど）。 その場合、これを（引数なしで呼ばれる）関数にして、:objectsのリストとして受け付ける値を返してください。

:columns

これは各要素が文字列（列名）か、（vtable-columnオブジェクトを作る）キーワード／バリューのplistか、完全なvtable-columnオブジェクトの何れかです。 vtable-columnオブジェクトには以下のスロットがあります。

name

列の名前。

width

列の幅。 以下の何れかを取れます。

数値n

‘nex’の形式の文字列

表のフェイスのn ‘x’ 文字の幅です。

‘npx’の形式の文字列

nピクセル。

‘n%’の形式の文字列

ウィンドウの幅のnパーセント。

widthが提供されていなければ、幅は（:objectsまたは:objects-functionを通じて提供される）列のデータ、あるいはデータがなければ窓の幅に基づいて計算されます。

min-width

widthと同じ書式を使いますが、最小幅を指定します（また、widthがこれより小さければwidthを上塗りします）。

max-width

This uses the same format as width, but specifies the maximum width (and overrides width if width is larger than this. min-width/max-width can be useful if width is given as a percentage of the window width, and you want to ensure that the column doesn’t grow pointlessly large or unreadably narrow.

primary

これが第一の列であるかです。 初期の整列に使われます。 ascendかdescendで、表がどちらの順で整列されるかを指定します。

getter

If present, this function will be called to return the column value.

Function: column-getter オブジェクト 表 ¶

It’s called with two parameters: the object and the table.

formatter

存在するとき、この関数を呼んで値を書式化します。

Function: column-formatter 値 ¶

列の値の1引数で呼ばれます。

displayer

If present, this function will be called to prepare the formatted value for display. This function should return a string with the table face applied, and also limit the width of the string to the display width.

Function: column-displayer fvalue max-width table ¶

fvalue is the formatted value; max-width is the maximum width (in pixels), and table is the table.

align

Should be either right or left. If not specified, numerical values will be flushed to the right, and all other values will be flushed to the left.

:getter

If given, this is a function that should return the values to use in the table, and will be called once for each element in the table (unless overridden by a column getter function).

Function: getter object index table ¶

For a simple object (like a sequence), this function will typically just return the element corresponding to the column index (zero-based), but the function can do any computation it wants. If it’s more convenient to write the function based on column names rather than the column index, the vtable-column function can be used to map from index to name.

:formatter

If present, this is a function that should format the value, and it will be called on all values in the table (unless overridden by a column formatter).

Function: formatter value index table ¶

This function is called with three parameters: the value (as returned by the getter); the column index, and the table. It can return any value.

This can be used to (for instance) format numbers in a human-readable form.

:displayer

Before displaying an element, it’s passed to the displaying function (if any).

Function: displayer fvalue index max-width table ¶

This is called with four arguments: the formatted value of the element (as returned by the formatter function); the column index; the display width (in pixels); and the table.

This function should return a string with the table face applied, and truncated to the display width.

This can be used to (for instance) change the size of images that are displayed in the table.

:use-header-line

nilでなければ（それが既定です）、見出し行に列名を表示します。 これがほとんどの場合でよくあることですが、表の前にバッファに別のテキストがあったり、同じバッファに複数の表があったりするときは、nilにしてください。

:face

The face to be used. This defaults to vtable. This face doesn’t override the faces in the data, or the faces supplied by the getter and formatter functions.

:row-colors

If present, this should be a list of color names to be used as the background color on the rows. If there are fewer colors here than there are rows, the rows will be repeated. The most common use case here is to have alternating background colors on the rows, so this would usually be a list of two colors. This can also be a list of faces to be used.

:column-colors

If present, this should be a list of color names to be used as the background color on the columns. If there are fewer colors here than there are columns, the colors will be repeated. The most common use case here is to have alternating background colors on the columns, so this would usually be a list of two colors. This can also be a list of faces to be used. If both :row-colors and :column-colors is present, the colors will be “blended” to produce the final colors in the table.

:actions

define-keymapと同じ構文が使われますが、命令を直接参照はしません。 各キーは現在のオブジェクトを選び出す命令に束縛され、指定された関数を引数として呼びます。

:keymap

表で使われるキーマップです。 この命令は通常通りに呼ばれ、現在の行に表示されているオブジェクトを扱うものであれば、vtable-current-object関数 (see ‘Interface Functions’) を使ってオブジェクトが何であるのかを調べられます。

:separator-width

The width of the blank space between columns. If not specified, it defaults to 1.

:divider-width

:divider

You can have a divider inserted between the columns. This can either be specified by using :divider, which should be a string to be displayed between the columns, or :divider-width, which specifies the width of the space to be used as the divider, in units of characters of the face used to display the table. If not specified, :divider defaults to nil, but specifying :divider-width effectively sets the divider to a whitespace string of that width.

:sort-by

This should be a list of tuples, and specifies how the table is to be sorted. Each tuple should consist of an integer (the column index) and either ascend or descend.

The table is first sorted by the first element in this list, and then the next, until the end is reached.

:ellipsis

By default, when shortening displayed values, an ellipsis will be shown. If this is nil, no ellipsis is shown. (The text to use as the ellipsis is determined by the truncate-string-ellipsis function.)

:insert ¶

既定では、make-vtableは表をその地点に挿入します。 これがnilであれば、何も挿入されませんが、vtableオブジェクトが返されます。 そして、後からvtable-insert関数で挿入できます。

make-tableはvtableオブジェクトを返します。 オブジェクトのスロットへは、上述のキーワードに基づく名前を持つアクセサ関数を使ってアクセスできます。 例えばフェイスにアクセスするにはvtable-faceを使います。

4 命令 ¶

地点がvtableに置かれていれば、以下のキーが束縛されます。

S ¶

現在の行で表を整列します (vtable-sort-by-current-column)。 なお表は、取得関数 (see ‘Making A Table’) によって返されるデータに従って昇順に整列されます。 バッファに表示されているものではありません。 数値データしかない列は数値として整列され、それ以外は文字列として整列されます。

{ ¶

現在の列を狭くします (vtable-narrow-current-column)。

} ¶

現在の列を広くします (vtable-widen-current-column)。

M-<left> ¶

前の列に移ります (vtable-previous-column)。

M-<right> ¶

次の列に移ります (vtable-next-column)。

g ¶

表を再生成します (vtable-revert-command)。 この命令は、表に:objects-functionがあり、新しいデータが取得できれば、効果があるでしょう。

5 インターフェース関数 ¶

vtableに基づくモードを書く必要があるなら、表を様々な方法で扱わなければなりません。 例えばオブジェクトを更新して結果を表示する命令を書く必要があります。 本章はそうした扱いをするための関数を説明します。

Function: vtable-current-table ¶

この関数は地点がある表を返します。

Function: vtable-current-object ¶

この関数は現在の行にあるオブジェクトを返します（なおこれは元のオブジェクトであって、バッファに表示されている文字ではありません）。

Function: vtable-current-column ¶

この関数は現在のバッファの現在の間隔の大きさを返します。

Function: vtable-goto-table 表 ¶

地点を表の始めに移してその位置を返します。 表が現在のバッファに見当たらなければ、地点を移さずnilを返します。

Function: vtable-goto-object オブジェクト ¶

オブジェクトが現在の表に表示されている行の最初に地点を移し、その位置を返します。 オブジェクトが見当たらなければ、地点を移さずnilを返します。

Function: vtable-goto-column 添字 ¶

添字番目の列の始めに地点を移します（最初の列はゼロ番目です）。

Function: vtable-beginning-of-table ¶

現在の表の始めに移ります。

Function: vtable-end-of-table ¶

現在の表の終わりに移ります。

Function: vtable-remove-object 表 オブジェクト ¶

表からオブジェクトを削除します。 これは表示されている表も更新します。

Function: vtable-insert-object 表 オブジェクト &optional 位置 前 ¶

Insert object into table. location should be an object in the table, the new object is inserted after this object, or before it if before is non-nil. If location is nil, object is appended to table, or prepended if before is non-nil.

location can also be an integer, a zero-based index into the table. In this case, object is inserted at that index. If the index is out of range, object is prepended to table if the index is too small, or appended if it is too large. In this case, before is ignored.

If table is empty, location and before are ignored.

This also updates the displayed table.

Function: vtable-update-object table object &optional old-object ¶

Update object’s representation in table. Optional argument old-object, if non-nil, means to replace old-object with object and redisplay the associated row in the table. In either case, if the existing object is not found in the table (being compared with equal), signal an error.

This has the same effect as calling vtable-remove-object and then vtable-insert-object, but is more efficient.

Note a limitation: if the table’s buffer is not in a visible window, or if its window has changed width since it was updated, updating the table is not possible, and an error is signaled.

Function: vtable-column 表 添字 ¶

表の添字番目の列の列名を返します。

6 GNU自由文書使用許諾 ¶

Copyright © 2000, 2001, 2002, 2007, 2008 Free Software Foundation, Inc.
https://fsf.org/

Everyone is permitted to copy and distribute verbatim copies
of this license document, but changing it is not allowed.

0. PREAMBLE

   The purpose of this License is to make a manual, textbook, or other functional and useful document free in the sense of freedom: to assure everyone the effective freedom to copy and redistribute it, with or without modifying it, either commercially or noncommercially. Secondarily, this License preserves for the author and publisher a way to get credit for their work, while not being considered responsible for modifications made by others.

   This License is a kind of “copyleft”, which means that derivative works of the document must themselves be free in the same sense. It complements the GNU General Public License, which is a copyleft license designed for free software.

   We have designed this License in order to use it for manuals for free software, because free software needs free documentation: a free program should come with manuals providing the same freedoms that the software does. But this License is not limited to software manuals; it can be used for any textual work, regardless of subject matter or whether it is published as a printed book. We recommend this License principally for works whose purpose is instruction or reference.

1. APPLICABILITY AND DEFINITIONS

   This License applies to any manual or other work, in any medium, that contains a notice placed by the copyright holder saying it can be distributed under the terms of this License. Such a notice grants a world-wide, royalty-free license, unlimited in duration, to use that work under the conditions stated herein. The “Document”, below, refers to any such manual or work. Any member of the public is a licensee, and is addressed as “you”. You accept the license if you copy, modify or distribute the work in a way requiring permission under copyright law.

   A “Modified Version” of the Document means any work containing the Document or a portion of it, either copied verbatim, or with modifications and/or translated into another language.

   A “Secondary Section” is a named appendix or a front-matter section of the Document that deals exclusively with the relationship of the publishers or authors of the Document to the Document’s overall subject (or to related matters) and contains nothing that could fall directly within that overall subject. (Thus, if the Document is in part a textbook of mathematics, a Secondary Section may not explain any mathematics.) The relationship could be a matter of historical connection with the subject or with related matters, or of legal, commercial, philosophical, ethical or political position regarding them.

   The “Invariant Sections” are certain Secondary Sections whose titles are designated, as being those of Invariant Sections, in the notice that says that the Document is released under this License. If a section does not fit the above definition of Secondary then it is not allowed to be designated as Invariant. The Document may contain zero Invariant Sections. If the Document does not identify any Invariant Sections then there are none.

   The “Cover Texts” are certain short passages of text that are listed, as Front-Cover Texts or Back-Cover Texts, in the notice that says that the Document is released under this License. A Front-Cover Text may be at most 5 words, and a Back-Cover Text may be at most 25 words.

   A “Transparent” copy of the Document means a machine-readable copy, represented in a format whose specification is available to the general public, that is suitable for revising the document straightforwardly with generic text editors or (for images composed of pixels) generic paint programs or (for drawings) some widely available drawing editor, and that is suitable for input to text formatters or for automatic translation to a variety of formats suitable for input to text formatters. A copy made in an otherwise Transparent file format whose markup, or absence of markup, has been arranged to thwart or discourage subsequent modification by readers is not Transparent. An image format is not Transparent if used for any substantial amount of text. A copy that is not “Transparent” is called “Opaque”.

   Examples of suitable formats for Transparent copies include plain ASCII without markup, Texinfo input format, LaTeX input format, SGML or XML using a publicly available DTD, and standard-conforming simple HTML, PostScript or PDF designed for human modification. Examples of transparent image formats include PNG, XCF and JPG. Opaque formats include proprietary formats that can be read and edited only by proprietary word processors, SGML or XML for which the DTD and/or processing tools are not generally available, and the machine-generated HTML, PostScript or PDF produced by some word processors for output purposes only.

   The “Title Page” means, for a printed book, the title page itself, plus such following pages as are needed to hold, legibly, the material this License requires to appear in the title page. For works in formats which do not have any title page as such, “Title Page” means the text near the most prominent appearance of the work’s title, preceding the beginning of the body of the text.

   The “publisher” means any person or entity that distributes copies of the Document to the public.

   A section “Entitled XYZ” means a named subunit of the Document whose title either is precisely XYZ or contains XYZ in parentheses following text that translates XYZ in another language. (Here XYZ stands for a specific section name mentioned below, such as “Acknowledgements”, “Dedications”, “Endorsements”, or “History”.) To “Preserve the Title” of such a section when you modify the Document means that it remains a section “Entitled XYZ” according to this definition.

   The Document may include Warranty Disclaimers next to the notice which states that this License applies to the Document. These Warranty Disclaimers are considered to be included by reference in this License, but only as regards disclaiming warranties: any other implication that these Warranty Disclaimers may have is void and has no effect on the meaning of this License.

2. VERBATIM COPYING

   You may copy and distribute the Document in any medium, either commercially or noncommercially, provided that this License, the copyright notices, and the license notice saying this License applies to the Document are reproduced in all copies, and that you add no other conditions whatsoever to those of this License. You may not use technical measures to obstruct or control the reading or further copying of the copies you make or distribute. However, you may accept compensation in exchange for copies. If you distribute a large enough number of copies you must also follow the conditions in section 3.

   You may also lend copies, under the same conditions stated above, and you may publicly display copies.

3. COPYING IN QUANTITY

   If you publish printed copies (or copies in media that commonly have printed covers) of the Document, numbering more than 100, and the Document’s license notice requires Cover Texts, you must enclose the copies in covers that carry, clearly and legibly, all these Cover Texts: Front-Cover Texts on the front cover, and Back-Cover Texts on the back cover. Both covers must also clearly and legibly identify you as the publisher of these copies. The front cover must present the full title with all words of the title equally prominent and visible. You may add other material on the covers in addition. Copying with changes limited to the covers, as long as they preserve the title of the Document and satisfy these conditions, can be treated as verbatim copying in other respects.

   If the required texts for either cover are too voluminous to fit legibly, you should put the first ones listed (as many as fit reasonably) on the actual cover, and continue the rest onto adjacent pages.

   If you publish or distribute Opaque copies of the Document numbering more than 100, you must either include a machine-readable Transparent copy along with each Opaque copy, or state in or with each Opaque copy a computer-network location from which the general network-using public has access to download using public-standard network protocols a complete Transparent copy of the Document, free of added material. If you use the latter option, you must take reasonably prudent steps, when you begin distribution of Opaque copies in quantity, to ensure that this Transparent copy will remain thus accessible at the stated location until at least one year after the last time you distribute an Opaque copy (directly or through your agents or retailers) of that edition to the public.

   It is requested, but not required, that you contact the authors of the Document well before redistributing any large number of copies, to give them a chance to provide you with an updated version of the Document.

4. MODIFICATIONS

   You may copy and distribute a Modified Version of the Document under the conditions of sections 2 and 3 above, provided that you release the Modified Version under precisely this License, with the Modified Version filling the role of the Document, thus licensing distribution and modification of the Modified Version to whoever possesses a copy of it. In addition, you must do these things in the Modified Version:

   1. Use in the Title Page (and on the covers, if any) a title distinct from that of the Document, and from those of previous versions (which should, if there were any, be listed in the History section of the Document). You may use the same title as a previous version if the original publisher of that version gives permission.
   2. List on the Title Page, as authors, one or more persons or entities responsible for authorship of the modifications in the Modified Version, together with at least five of the principal authors of the Document (all of its principal authors, if it has fewer than five), unless they release you from this requirement.
   3. State on the Title page the name of the publisher of the Modified Version, as the publisher.
   4. Preserve all the copyright notices of the Document.
   5. Add an appropriate copyright notice for your modifications adjacent to the other copyright notices.
   6. Include, immediately after the copyright notices, a license notice giving the public permission to use the Modified Version under the terms of this License, in the form shown in the Addendum below.
   7. Preserve in that license notice the full lists of Invariant Sections and required Cover Texts given in the Document’s license notice.
   8. Include an unaltered copy of this License.
   9. Preserve the section Entitled “History”, Preserve its Title, and add to it an item stating at least the title, year, new authors, and publisher of the Modified Version as given on the Title Page. If there is no section Entitled “History” in the Document, create one stating the title, year, authors, and publisher of the Document as given on its Title Page, then add an item describing the Modified Version as stated in the previous sentence.
   10. Preserve the network location, if any, given in the Document for public access to a Transparent copy of the Document, and likewise the network locations given in the Document for previous versions it was based on. These may be placed in the “History” section. You may omit a network location for a work that was published at least four years before the Document itself, or if the original publisher of the version it refers to gives permission.
   11. For any section Entitled “Acknowledgements” or “Dedications”, Preserve the Title of the section, and preserve in the section all the substance and tone of each of the contributor acknowledgements and/or dedications given therein.
   12. Preserve all the Invariant Sections of the Document, unaltered in their text and in their titles. Section numbers or the equivalent are not considered part of the section titles.
   13. Delete any section Entitled “Endorsements”. Such a section may not be included in the Modified Version.
   14. Do not retitle any existing section to be Entitled “Endorsements” or to conflict in title with any Invariant Section.
   15. Preserve any Warranty Disclaimers.

   If the Modified Version includes new front-matter sections or appendices that qualify as Secondary Sections and contain no material copied from the Document, you may at your option designate some or all of these sections as invariant. To do this, add their titles to the list of Invariant Sections in the Modified Version’s license notice. These titles must be distinct from any other section titles.

   You may add a section Entitled “Endorsements”, provided it contains nothing but endorsements of your Modified Version by various parties—for example, statements of peer review or that the text has been approved by an organization as the authoritative definition of a standard.

   You may add a passage of up to five words as a Front-Cover Text, and a passage of up to 25 words as a Back-Cover Text, to the end of the list of Cover Texts in the Modified Version. Only one passage of Front-Cover Text and one of Back-Cover Text may be added by (or through arrangements made by) any one entity. If the Document already includes a cover text for the same cover, previously added by you or by arrangement made by the same entity you are acting on behalf of, you may not add another; but you may replace the old one, on explicit permission from the previous publisher that added the old one.

   The author(s) and publisher(s) of the Document do not by this License give permission to use their names for publicity for or to assert or imply endorsement of any Modified Version.

5. COMBINING DOCUMENTS

   You may combine the Document with other documents released under this License, under the terms defined in section 4 above for modified versions, provided that you include in the combination all of the Invariant Sections of all of the original documents, unmodified, and list them all as Invariant Sections of your combined work in its license notice, and that you preserve all their Warranty Disclaimers.

   The combined work need only contain one copy of this License, and multiple identical Invariant Sections may be replaced with a single copy. If there are multiple Invariant Sections with the same name but different contents, make the title of each such section unique by adding at the end of it, in parentheses, the name of the original author or publisher of that section if known, or else a unique number. Make the same adjustment to the section titles in the list of Invariant Sections in the license notice of the combined work.

   In the combination, you must combine any sections Entitled “History” in the various original documents, forming one section Entitled “History”; likewise combine any sections Entitled “Acknowledgements”, and any sections Entitled “Dedications”. You must delete all sections Entitled “Endorsements.”

6. COLLECTIONS OF DOCUMENTS

   You may make a collection consisting of the Document and other documents released under this License, and replace the individual copies of this License in the various documents with a single copy that is included in the collection, provided that you follow the rules of this License for verbatim copying of each of the documents in all other respects.

   You may extract a single document from such a collection, and distribute it individually under this License, provided you insert a copy of this License into the extracted document, and follow this License in all other respects regarding verbatim copying of that document.

7. AGGREGATION WITH INDEPENDENT WORKS

   A compilation of the Document or its derivatives with other separate and independent documents or works, in or on a volume of a storage or distribution medium, is called an “aggregate” if the copyright resulting from the compilation is not used to limit the legal rights of the compilation’s users beyond what the individual works permit. When the Document is included in an aggregate, this License does not apply to the other works in the aggregate which are not themselves derivative works of the Document.

   If the Cover Text requirement of section 3 is applicable to these copies of the Document, then if the Document is less than one half of the entire aggregate, the Document’s Cover Texts may be placed on covers that bracket the Document within the aggregate, or the electronic equivalent of covers if the Document is in electronic form. Otherwise they must appear on printed covers that bracket the whole aggregate.

8. TRANSLATION

   Translation is considered a kind of modification, so you may distribute translations of the Document under the terms of section 4. Replacing Invariant Sections with translations requires special permission from their copyright holders, but you may include translations of some or all Invariant Sections in addition to the original versions of these Invariant Sections. You may include a translation of this License, and all the license notices in the Document, and any Warranty Disclaimers, provided that you also include the original English version of this License and the original versions of those notices and disclaimers. In case of a disagreement between the translation and the original version of this License or a notice or disclaimer, the original version will prevail.

   If a section in the Document is Entitled “Acknowledgements”, “Dedications”, or “History”, the requirement (section 4) to Preserve its Title (section 1) will typically require changing the actual title.

9. TERMINATION

   You may not copy, modify, sublicense, or distribute the Document except as expressly provided under this License. Any attempt otherwise to copy, modify, sublicense, or distribute it is void, and will automatically terminate your rights under this License.

   However, if you cease all violation of this License, then your license from a particular copyright holder is reinstated (a) provisionally, unless and until the copyright holder explicitly and finally terminates your license, and (b) permanently, if the copyright holder fails to notify you of the violation by some reasonable means prior to 60 days after the cessation.

   Moreover, your license from a particular copyright holder is reinstated permanently if the copyright holder notifies you of the violation by some reasonable means, this is the first time you have received notice of violation of this License (for any work) from that copyright holder, and you cure the violation prior to 30 days after your receipt of the notice.

   Termination of your rights under this section does not terminate the licenses of parties who have received copies or rights from you under this License. If your rights have been terminated and not permanently reinstated, receipt of a copy of some or all of the same material does not give you any rights to use it.

10. FUTURE REVISIONS OF THIS LICENSE

    The Free Software Foundation may publish new, revised versions of the GNU Free Documentation License from time to time. Such new versions will be similar in spirit to the present version, but may differ in detail to address new problems or concerns. See https://www.gnu.org/licenses/.

    Each version of the License is given a distinguishing version number. If the Document specifies that a particular numbered version of this License “or any later version” applies to it, you have the option of following the terms and conditions either of that specified version or of any later version that has been published (not as a draft) by the Free Software Foundation. If the Document does not specify a version number of this License, you may choose any version ever published (not as a draft) by the Free Software Foundation. If the Document specifies that a proxy can decide which future versions of this License can be used, that proxy’s public statement of acceptance of a version permanently authorizes you to choose that version for the Document.

11. RELICENSING

    “Massive Multiauthor Collaboration Site” (or “MMC Site”) means any World Wide Web server that publishes copyrightable works and also provides prominent facilities for anybody to edit those works. A public wiki that anybody can edit is an example of such a server. A “Massive Multiauthor Collaboration” (or “MMC”) contained in the site means any set of copyrightable works thus published on the MMC site.

    “CC-BY-SA” means the Creative Commons Attribution-Share Alike 3.0 license published by Creative Commons Corporation, a not-for-profit corporation with a principal place of business in San Francisco, California, as well as future copyleft versions of that license published by that same organization.

    “Incorporate” means to publish or republish a Document, in whole or in part, as part of another Document.

    An MMC is “eligible for relicensing” if it is licensed under this License, and if all works that were first published under this License somewhere other than this MMC, and subsequently incorporated in whole or in part into the MMC, (1) had no cover texts or invariant sections, and (2) were thus incorporated prior to November 1, 2008.

    The operator of an MMC Site may republish an MMC contained in the site under CC-BY-SA on the same site at any time before August 1, 2009, provided the MMC is eligible for relicensing.

ADDENDUM: How to use this License for your documents ¶

To use this License in a document you have written, include a copy of the License in the document and put the following copyright and license notices just after the title page:

  Copyright (C)  year  your name.
  Permission is granted to copy, distribute and/or modify this document
  under the terms of the GNU Free Documentation License, Version 1.3
  or any later version published by the Free Software Foundation;
  with no Invariant Sections, no Front-Cover Texts, and no Back-Cover
  Texts.  A copy of the license is included in the section entitled ``GNU
  Free Documentation License''.

If you have Invariant Sections, Front-Cover Texts and Back-Cover Texts, replace the “with…Texts.” line with this:

    with the Invariant Sections being list their titles, with
    the Front-Cover Texts being list, and with the Back-Cover Texts
    being list.

If you have Invariant Sections without Cover Texts, or some other combination of the three, merge those two alternatives to suit the situation.

If your document contains nontrivial examples of program code, we recommend releasing these examples in parallel under your choice of free software license, such as the GNU General Public License, to permit their use in free software.