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## Phrase Level Elements

### Font Styles

    ['italic], [*bold], [_underline], [^teletype], [-strikethrough]

will generate:

italic, bold, underline, `teletype`, strikethrough

Like all non-terminal phrase level elements, this can of course be nested:

    [*['bold-italic]]

will generate:

bold-italic

### Replaceable

When you want content that may or must be replaced by the user, use the syntax:

    [~replacement]

This will generate:

`replacement`

### Quotations

    ["A question that sometimes drives me hazy: am I or are the others crazy?]--Einstein

will generate:

“A question that sometimes drives me hazy: am I or are the others crazy?”--Einstein

Note the proper left and right quote marks. Also, while you can simply use ordinary quote marks like "quoted", our quotation, above, will generate correct DocBook quotations (e.g. <quote>quoted</quote>).

Like all phrase elements, quotations may be nested. Example:

    ["Here's the rule for bargains: ["Do other men, for they would do you.] That's
    the true business precept.]

will generate:

“Here's the rule for bargains: ‘Do other men, for they would do you.’ That's the true business precept.”

### Simple formatting

Simple markup for formatting text, common in many applications, is now supported:

    /italic/, *bold*, _underline_, =teletype=

will generate:

italic, bold, underline, `teletype`

Unlike QuickBook's standard formatting scheme, the rules for simpler alternatives are much stricter[9].

- Simple markups cannot nest. You can combine a simple markup with a nestable markup.
- Simple markups cannot contain any other form of quickbook markup.
- A non-space character must follow the leading markup
- A non-space character must precede the trailing markup
- A space or a punctuation must follow the trailing markup
- If the matching markup cannot be found within a block, the formatting will not be applied. This is to ensure that un-matched formatting markups, which can be a common mistake, does not corrupt anything past a single block. We do not want the rest of the document to be rendered bold just because we forgot a trailing '*'. A single block is terminated by two end of lines or the close bracket: ']'.
- A line starting with the star will be interpreted as an unordered list. See Unordered lists.

Table 37.1. More Formatting Samples

Markup | Result
--- | ---
`*Bold*` | Bold
`*Is bold*` | Is bold
`* Not bold* *Not bold * * Not bold *` | * Not bold* *Not bold * * Not bold *
`This*Isn't*Bold (no bold)` | This*Isn't*Bold (no bold)
`(*Bold Inside*) (parenthesis not bold)` | (Bold Inside) (parenthesis not bold)
`*(Bold Outside)* (parenthesis bold)` | (Bold Outside) (parenthesis bold)
`3*4*5 = 60 (no bold)` | 3*4*5 = 60 (no bold)
`3 * 4 * 5 = 60 (no bold)` | 3 * 4 * 5 = 60 (no bold)
`3 *4* 5 = 60 (4 is bold)` | 3 4 5 = 60 (4 is bold)
`*This is bold* this is not *but this is*` | This is bold this is not but this is
`*This is bold*.` | This is bold.
`*B*. (bold B)` | B. (bold B)
`['*Bold-Italic*]` | Bold-Italic
`*side-by*/-side/` | side-by-side

As mentioned, simple markups cannot go past a single block. The text from "have" to "full" in the following paragraph will be rendered as bold:

    Baa baa black sheep, *have you any wool?
    Yes sir, yes sir, three bags full!*
    One for the master, one for the dame,
    And one for the little boy who lives down the lane.

Baa baa black sheep, have you any wool? Yes sir, yes sir, three bags full! One for the master, one for the dame, And one for the little boy who lives down the lane.

But in the following paragraph, bold is not applied:

    Baa baa black sheep, *have you any wool?
    Yes sir, yes sir, three bags full!
    One for the master, one for the dame,
    And one for the little boy who lives down the lane.

Baa baa black sheep, *have you any wool? Yes sir, yes sir, three bags full! One for the master, one for the dame, And one for the little boy who lives down the lane.

### Inline code

Inlining code in paragraphs is quite common when writing C++ documentation. We provide a very simple markup for this. For example, this:

    This text has inlined code `int main() { return 0; }` in it.

will generate:

This text has inlined code `int main() { return 0; }` in it. The code will be syntax highlighted.

| Note
We simply enclose the code with the tick: `"`"`, not the single quote: `"'"`. Note too that ``some code`` is preferred over `[^some code]`.

### Code blocks

Preformatted code simply starts with a space or a tab (See Code). However, such a simple syntax cannot be used as phrase elements in lists (See Ordered lists and Unordered lists), tables (See Tables), etc. Inline code (see above) can. The problem is, inline code does not allow formatting with newlines, spaces, and tabs. These are lost.

We provide a phrase level markup that is a mix between the two. By using the double-tick or triple-tick, instead of the single-tick, we are telling QuickBook to use preformatted blocks of code. Example:

    ``
        #include <iostream>

        int main()
        {
            std::cout << "Hello, World!" << std::endl;
            return 0;
        }
    ``

or:

    ```
        #include <iostream>

        int main()
        {
            std::cout << "Hello, World!" << std::endl;
            return 0;
        }
    ```

will generate:

    #include <iostream>

    int main()
    {
        std::cout << "Hello, World!" << std::endl;
        return 0;
    }

### Source Mode

If a document contains more than one type of source code then the source mode may be changed dynamically as the document is processed. All QuickBook documents are initially in C++ mode by default, though an alternative initial value may be set in the Document section.

To change the source mode, use the `[source-mode]` markup, where `source-mode` is one of the supported modes. For example, this:

    Python's [python] `import` is rather like C++'s [c++] `#include`. A
    C++ comment `// looks like this` whereas a Python comment [python]
    `# looks like this`.

will generate:

Python's `import` is rather like C++'s `#include`. A C++ comment `// looks like this` whereas a Python comment `#looks like this`.

Table 37.2. Supported Source Modes

Mode | Source Mode Markup
--- | ---
C++ | `[c++]`
Python | `[python]`
Plain Text | `[teletype]`

| Note
The source mode strings are lowercase.

### line-break

    [br]

| Warning
`[br]` generates invalid docbook. It seems to mostly work okay but there might be problems, especially when using an alternative docbook processor.

### Anchors

    [#named_anchor]

A named anchor is a hook that can be referenced by a link elsewhere in the document. You can then reference an anchor with `[link named_anchor Some link text]`. See Anchor links, Section and Heading.

These anchors are global and can be accessed from anywhere in the quickbook documentation. Be careful to avoid clashes with anchors in other sections.

### Links

    [@http://www.boost.org this is [*boost's] website....]

will generate:

this is boost's website....

URL links where the link text is the link itself is common. Example:

    see http://spirit.sourceforge.net/

so, when the text is absent in a link markup, the URL is assumed. Example:

    see [@http://spirit.sourceforge.net/]

will generate:

see http://spirit.sourceforge.net/

Boostbook also support a custom url schema for linking to files within the boost distribution:

    [@boost:/libs/spirit/index.html the Boost.Spirit documentation]

will generate: the Boost.Spirit documentation

Note that this is only available when using BoostBook, and only for links - it can't be used for images.

### Anchor links

You can link within a document using:

    [link document_id.section_id.normalized_header_text The link text]

See sections Section and Heading for more info.

### refentry links

In addition, you can link internally to an XML refentry like:

    [link xml.refentry The link text]

This gets converted into `<link linkend="xml.refentry">The link text</link>`.

Like URLs, the link text is optional. If this is not present, the link text will automatically be the refentry. Example:

    [link xml.refentry]

This gets converted into `<link linkend="xml.refentry">xml.refentry</link>`.

### Code Links

If you want to link to a function, class, member, enum, concept, global, or header in the reference section, you can use:

    [funcref fully::qualified::function_name The link text]
    [classref fully::qualified::class_name The link text]
    [memberref fully::qualified::member_name The link text]
    [enumref fully::qualified::enum_name The link text]
    [macroref MACRO_NAME The link text]
    [conceptref ConceptName The link text]
    [headerref path/to/header.hpp The link text]
    [globalref fully::qualified::global The link text]

Again, the link text is optional. If this is not present, the link text will automatically be the function, class, member, enum, macro, concept, global, or header name. Example:

    [classref boost::bar::baz]

would have "boost::bar::baz" as the link text.

### Escape

The escape mark-up is used when we don't want to do any processing.

    '''
    escape (no processing/formatting)
    '''

Escaping allows us to pass XML markup to BoostBook or DocBook. For example:

    '''
    <emphasis role="bold">This is direct XML markup</emphasis>
    '''

This is direct XML markup

| Important
Be careful when using the escape. The text must conform to BoostBook/DocBook syntax.

### Single char escape

The backslash may be used to escape a single punctuation character. The punctuation immediately after the backslash is passed without any processing. This is useful when we need to escape QuickBook punctuations such as `[` and `]`. For example, how do you escape the triple quote? Simple: `\'\'\'`

`\n` has a special meaning. It is used to generate line breaks.

| Warning
`\n` is now deprecated, use `[br]` instead. Although, use it sparingly as it can generated invalid docbook

The escaped space: `\` also has a special meaning. The escaped space is removed from the output.

### Unicode escape

You can enter any 16-bit unicode character by using `\u` followed by its 4 digit hexadecimal code, or a 32-bit character by using `\U` followed by an 8 digit hexadecimal code. eg.

    \u03B1 + \u03B2

will generate:

> α + β

### Images

    [$image.jpg]

From version 1.5, you can also use DocBook imagedata attributes:

    [$image.jpg [width 200in] [height 200in]]

### Footnotes

As of version 1.3, QuickBook supports footnotes. Just put the text of the footnote in a `[footnote]` block, and the text will be put at the bottom of the current page. For example, this:

    [footnote A sample footnote]

will generate this[10].

### Macro Expansion

    __a_macro_identifier__

See Macros for details.

### Template Expansion

    [a_template_identifier]

See Templates for details.

### Conditional Generation

Like C++ `#ifdef`, you can generate phrases depending on the presence of a macro. Example:

    [? __to_be__ To be or not to be]

Here, the phrase "To be or not to be" will only be generated if the macro symbol `__to_be__` has been previously defined. The phrase above will not do anything since we haven't defined `__to_be__`. Now, let's define the symbol:

    [def __to_be__]

And try again:

To be or not to be

Yes!

[9] Thanks to David Barrett, author of Qwiki, for sharing these samples and teaching me these obscure formatting rules. I wasn't sure at all if Spirit, being more or less a formal EBNF parser, can handle the context sensitivity and ambiguity.

[10] A sample footnote