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include homepage.en.yhtml2

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page "The Features" {

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    h2 id=text > Text

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    p   >>

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        To output text nodes (¬http://www.w3.org/TR/2008/REC-xml-20081126/#syntax character data¬),

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        write literals. There are integer literals, floating point literals and text literals.

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        >>

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    p   >>

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        Literals are written

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        ¬http://docs.python.org/reference/lexical_analysis.html#id7 like in Python¬,

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        that means, text literals are in single or double quotes, or multiline

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        in triple double quotes:

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        >>

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    Code    ||

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            "text" 'also text' """some more text"""

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            42 "an integer and" 42.23 "a floating point literal"

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            ||

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    p   >>

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        Literals are being output by the ¬#textfunction text function¬.

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        >>

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    h2 id=functioncalls > Function Calls

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    p   >>

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        The main idea of YML scripts is calling functions which then generate

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        XML tags (¬http://www.w3.org/TR/2008/REC-xml-20081126/#syntax Markup¬).

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        Functions are generating single tags, lists or trees of tags.

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        >>

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        To call a function, write the name of the function, followed by a comma separated list

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        of function parameters (C like syntax) or just «attribute=value» pairs. Unlike C, you don't

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        need to insert the parameter list into parentheses. A simple function call can be terminated

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        by a semicolon «;» or by a period «.»

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        >>

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        It does not matter, if you're calling your function using parentheses or brackets or without.

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        So these statements are equal:

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        >>

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    Code    ||

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            foo "hello, world";

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            foo "hello, world".

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            foo("hello, world");

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            foo["hello, world"];

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            ||

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    h3 id=subtree > Subtrees

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        If you omit the tailing semicolon, you're creating a Subtree; YML Subtrees can also be

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        opened and closed with braces:

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        >>

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    Code    ||

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            foo {

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                bar {

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                    something;

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                }

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            }

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            ||

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    p > If a Subtree only consists of one single subelement, then you may omit the braces:

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    Code    ||

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            foo

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                bar;

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            ||

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    h3 id=named > Named Parameters

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        To generate ¬http://www.w3.org/TR/2008/REC-xml-20081126/#attdecls attributes¬ by calling

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        a function, you can use Named Parameters.

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        >>

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        For that case, assign literals or symbols to attribute names like the following.

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        The name of the parameter then will be used as the name of the generated attribute.

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        An example:

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        >>

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    Code    ||

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            div id=sample {

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                "this is a " a href="#sample" "link sample"

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            }

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            ||

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    p > This generates:

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    Code | <div id="sample">this is a <a href="#sample">link sample</a></div>

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    h3 > Unnamed Parameters

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        Unnamed Parameters prepare values for predefined attributes. The following example is

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        equivalent to the sample above:

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        >>

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    Code    ||

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            decl a(href);

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            decl div(id);

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            div "sample" {

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                "this is a " a "#sample" "link sample"

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            }

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            ||

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    p > If no predefined attribute can be allocated, the value of the parameter is added to the body.

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    h3 > Calling with &

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        Especially if you have a ¬#defaultbody default body¬ for your function, calling with

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        a leading «&» can be sensible: then the tag itself is omitted and only the body is being output:

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        >>

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    Code    ||

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            decl something { tag1; tag2; };

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            list {

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                &something;

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            }

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            ||

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    p > results in:

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    Code    ||

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            <list>

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              <tag1/>

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              <tag2/>

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            </list>

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            ||

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    p   >>

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        This has the same result as ¬#alias aliasing¬ «something» to «-».

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        >>

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    h3 id=funclist > Function Lists

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        Function Lists are a feature of YML to simulate a more C like syntax. Let's have some

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        examples. You can have a list of functions whereever you can have a function. Function

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        Lists are comma separated:

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        >>

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    Code    ||

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            x i, j, k

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            ||

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    p > compiles to:

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    Code    ||

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            <x>

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              <i/>

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              <j/>

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              <k/>

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            </x>

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            ||

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    h3 id=paramlists > Parameter Lists

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        A sample together with ¬#descending Descending Attributes¬:

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        >>

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    Code    ||

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            decl Interface @name;

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            decl attr @type @name;

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            decl func @type @name;

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            Interface Icecream {

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                attr color flavour;

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                attr long number;

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                func int getPrice();

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                func void addFlavour(in color flavour, in long number);

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            }

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            ||

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    p > compiles to:

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    Code    ||

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            <Interface name="Icecream">

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              <attr type="color" name="flavour"/>

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              <attr type="long" name="number"/>

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              <func type="int" name="getPrice"/>

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              <func type="void" name="addFlavour">

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                <parm>

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                  <in/>

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                  <color/>

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                  <flavour/>

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                </parm>

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                <parm>

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                  <in/>

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                  <long/>

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                  <number/>

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                </parm>

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              </func>

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            </Interface>

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            ||

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    p   >>

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        Note the «parm» tags – they're generated by default, if you write a Parameter List

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        behind a Function Call. That differs from calling the function with parameters –

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        ¬#functioncalls calling¬ means using ¬#text text¬ values.

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        >>

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        The «parm» tags are emitted, because the «_parm» function is called each time

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        such a parameter will be emitted.

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        >>

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    p   >>

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        If you want to have the «_parm» function doing other things, just ¬#decl declare¬

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        it in another way.

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        >>

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    h3 id=generics > Generic Declarations

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        Using Generic Declarations is just like using ¬#paramlists Parameter Lists¬ – use angle brackets

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        instead of parentheses. For Generic Declarations, the «_generic» function is called each

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        time such a Generic Declaration will be emitted, generating «generic» tags as the default:

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        >>

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    Code | max<int>(x, y)

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    p > compiles to:

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    Code    ||

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            <max>

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              <generic>

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                <int/>

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              </generic>

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              <parm>

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                <x/>

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              </parm>

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              <parm>

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                <y/>

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              </parm>

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            </max>

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            ||

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    h3 id=contentfc > The «content» function

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        The «content;» Function Call has a special meaning (only in a ¬#defaultbody default body¬):

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        it does not generate a tag, but instead

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        the tags of a supplied body in a call will be inserted at each place where the «content;»

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        function call is existing in the ¬#defaultbody default body¬.

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        >>

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    h3 id=textfunction > The «text» function

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        There is a special YML function named «text». Usually, it's just ¬#alias aliased¬ to «-» (and 

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        therefore outputting nothing). The «text» function is called each time a text literal will be

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        output.

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        >>

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    p   >>

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        If you ¬#decl declare¬ the «text» function, you can overload that behaviour. For example,

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        ¬yslt YSLT¬ is declaring «text» like this:

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        >>

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    Code    ||

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            decl text alias xsl:text;

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            "test"

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            ||

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    p > generates:

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    Code | <xsl:text>test</xsl:text>

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        The «text» function is not called, if you give text as a value for an attribute:

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        >>

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    Code    ||

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            decl text alias xsl:text;

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            a "test"

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            ||

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    p > generates:

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    Code | <a>test</a>

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    p   >>

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        But it is called using the quoting operators:

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        >>

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    Code    ||

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            decl text alias xsl:text;

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            a > test

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            ||

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    p > generates:

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    Code | <a><xsl:text>test</xsl:text></a>

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    h3 id=declfunction > The «decl», «define» and «operator» functions

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        The «decl», «define» and «operator» functions are not defined, so they cannot be used

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        accidentally by having a syntax error i.e. in a «decl» statement. If you want to use such

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        a function, i.e. «decl()», you have to ¬#decl declare it explicitely¬:

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        >>

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    Code    ||

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            decl decl;

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            decl();

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            ||

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    p > will result in:

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    Code | <decl/>

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    h2 id=decl > Declaring Functions: decl

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        As default, each Function Call generates one XML tag, which has the same name. To be exact,

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        the XML tag has dashes in it's name where the YML function has underscores.

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        >>

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        To define, how tags and attributes look like, which are created by a Function Call, you

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        can use the «decl» statement.

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        >>

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    h3 > Trivial Declarations

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    p > In a trivial declaration, you're just declaring the Function Name and so the XML tag name:

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    Code | decl html, head, title, body, p, a;

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    p > As seen in the example, multiple declarations can be done in a comma separated list.

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        Because trivial declarations are done automatically, if you're using a function for the

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        first time, you usually don't need to declare this way.

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        >>

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    h3 > Specifying Unnamed Parameters

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        To specifiy Unnamed Parameters, give the parameter list comma separated in parentheses

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        or provide one or more brackets with parameter lists in them:

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        >>

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    Code | decl a(href), img[src];

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        If you're using the corresponding functions a() and img() together with an unnamed parameter

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        in a call, then these attributes are used for applying the values, respectively:

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        >>

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    Code | a "http://www.ccc.de" "The Club Homepage" img "logo.png";

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    p > These Function Calls generate:

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    Code | <a href="http://www.ccc.de">The Club Homepage</a><img src="logo.png"/>

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    h3 id=defaultattr > Giving Default Values for parameters

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        To give default values for generating XML attributes, assign a literal to each named parameter

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        in the declaration parentheses or brackets. Two examples, which do the same:

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    Code

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        ||

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        decl img(src, alt="picture");

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        decl img[src][alt="picture"];

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        ||

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    h3 id=alias > Aliasing: using different YML functions for the same XML tag for different tasks

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        Sometimes tags are used in different ways to do different things. For this case, you can

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        use aliasing. Aliasing means, the YML function name and the XML tag name differ. For example:

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        >>

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    Code | decl a(href), target(name) alias a;

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    p > Both defined YML functions then generate «<a />» tags – but the Unnamed Parameter differs.

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        The alias name «-» has a special meaning: it omits the tag in the output. That is especially

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        sensible if you have a ¬#defaultbody default body¬. Then an alias to «-» has the same meaning

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        as starting the function call with the «&» character: only the body is emitted.

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        >>

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    h3 id=descending > Specifying Descending Attributes

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        Maybe you want to write something like this:

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        >>

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    Code    ||

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            Module ERP {

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                Interface Customer {

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                    // ...

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                }

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            }

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            ||

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    p > Without any extras, this compiles to:

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    Code    ||

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            <Module>

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                <ERP>

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                    <Interface>

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                        <Customer />

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                    </Interface>

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                </ERP>

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            </Module>

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            ||

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    p   >>

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        For this case, it would be practical, if «ERP» would not be interpreted as extra tag

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        but as value for an attribute «name». This you can achive with Descending Attributes:

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        >>

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    Code | decl Module @name, Interface @name;

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    p > With this declaration, the code sample above is compiling to:

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    Code    ||

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            <Module name="ERP">

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                <Interface name="Customer" />

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            </Module>

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            ||

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    p   >>

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        Descending attributes can also be used this way:

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        >>

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    Code    ||

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            decl module +name;

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            decl element +name;

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            module Some {

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                element {

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                    one;

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                    two;

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                    three;

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                }

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                element {

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                    four; five; six

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                }

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            }

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            ||

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    p   >>

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        The above generates:

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        >>

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    Code    ||

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            <?xml version='1.0' encoding='UTF-8'?>

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            <module name="Some">

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              <element name="one"/>

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              <element name="two"/>

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              <element name="three"/>

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              <element name="four"/>

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              <element name="five"/>

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              <element name="six"/>

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            </module>

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            ||

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    h3 id=descending_pointer > Specifying Descending Pointers

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        Like with descending attributes, you can use descending ¬#pointer pointers¬. Instead of preceding the

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        name of an attribute with a «+» sign (like with ¬#descending descending attributes¬), precede it with an asterisk «*».

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        >>

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    p   >>

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        Like with ¬#pointer pointers¬ in general, it's a good idea to combine that with a ¬#defaultbody default body¬:

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        >>

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    Code    ||

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            decl f *p { some tags with *p };

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            f value;

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            ||

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        This generates:

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        >>

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    Code    ||

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            <?xml version='1.0' encoding='UTF-8'?>

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            <f>

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              <some>

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                <tags>

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                  <with>value</with>

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                </tags>

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              </some>

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            </f>

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            ||

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    h3 id=defaultbody > Supplying a Default Body

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        Additionally, you can supply a Default Body for each tag. For that case, add a YML function

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        block in braces to your declaration:

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        >>

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    Code    ||

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            decl pageContent alias body {

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                a name=top;

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                include heading.en.yhtml2;

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                div id=entries

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                content;

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            };

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            ||

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    p > The sample above is used for generating this homepage, for example.

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    p > See the ¬#contentfc content function¬.

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