docs: Include files are always searched at standard location, too.
This removes the need to specify the location where yml2 was unpacked or
installed as YML_PATH. So this now works:
YML_PATH=/foo ./yml2proc --xml2yml
The standard system location <prefix>/share/yml2 is now always appended to
the include search path. If this path does not exist, the directory one
above the `backend.py` file is added, allowing the same behaviour for
uninstalled yml2.
In the Makefile enforce the .ysl2 files to be searched in the current
directory first.
// the YML homepage
include homepage.en.yhtml2
page "YML – Why a Markup Language?!" {
h1 > Introduction
h2 > What is YML?
p >>
Well, it's the idea not to need to define a grammar first when you want to use a
¬http://en.wikipedia.org/wiki/Domain_Specific_Language Domain Specific Language¬.
For that purpose, YML is being translated into XML. Let's make an example.
>>
p >>
Everything which comes close to a C like language, parses without a grammar
definition:
>>
p > This:
Code
||
template< class T > T max(T a, T b);
||
p > Parses to:
Code
||
<?xml version='1.0' encoding='UTF-8'?>
<template>
<generic>
<class/>
<T/>
</generic>
<T>
<max>
<parm>
<T/>
<a/>
</parm>
<parm>
<T/>
<b/>
</parm>
</max>
</T>
</template>
||
p >>
Instead of defining grammars, you test out and play around until the
results are matching your needs. If the resulting tree does not fit
what you're expecting, change it by patching the grammar with `code > decl`:
>>
p > This:
Code
||
module A {
interface B {
attribute long n;
};
};
||
p > Parses to:
Code
||
<?xml version='1.0' encoding='UTF-8'?>
<module>
<A>
<interface>
<B>
<attribute>
<long>
<n/>
</long>
</attribute>
</B>
</interface>
</A>
</module>
||
p >>
This does not look like what we want. So we tell YML that
we have a module name after the module, an interface name after
the interface and type and name after the attribute:
>>
p > This:
Code
||
decl module @name;
decl interface @name;
decl attribute @type @name;
module A {
interface B {
attribute long n;
};
};
||
p > Parses to:
Code
||
<?xml version='1.0' encoding='UTF-8'?>
<module name="A">
<interface name="B">
<attribute type="long" name="n"/>
</interface>
</module>
||
h2 id=what > What can I do with YML?
p > With YML you can:
ul {
li p > use a C-like ¬http://en.wikipedia.org/wiki/Domain-specific_language DSL¬ without writing a grammar first
li p > generate code out of this ¬http://en.wikipedia.org/wiki/Domain-specific_language DSL¬ using ¬yslt YSLT¬
li p > generate code out of ¬http://en.wikipedia.org/wiki/Unified_Modeling_Language UML¬ using ¬yslt YSLT¬ on ¬http://en.wikipedia.org/wiki/XML_Metadata_Interchange XMI¬
li p > generate code out of any XML based language like ¬http://en.wikipedia.org/wiki/Scalable_Vector_Graphics SVG¬ using ¬yslt YSLT¬
li p > define a ¬http://en.wikipedia.org/wiki/Wiki wiki¬ like language in just a few lines like ¬http://fdik.org/yml/programming#wiki YHTML¬ does
li p > replace bad designed and complicated XML languages with simpler C-like ones
li p > ... and much more.
}
h2 id=howitworks > How it works: Replacing angle brackets with some Python
p > Just writing down what I wanted to have instead of XML for a sample:
Code ||
<list name="List of goods">
<head>
<columTitle>
Goods
</columnTitle>
<columnTitle>
Price
</columnTitle>
</head>
<row>
<value>
Beer
</value>
<value>
20
</value>
</row>
<row>
<value>
Wine
</value>
<value>
30
</value>
</row>
</list>
||
p > Something like that should be more easy, say, like this:
Code ||
list "List of goods" {
head title "Goods", title "Price";
row value "Beer", value 20;
row value "Wine", value 30;
}
||
h2 id=ylanguages > Y Languages
p >>
The latter is what I call an Y language – a language specified in YML. How could this be
achieved? Well, what's to do? To have the required information, how to build XML from the
script above, we need:
>>
ul {
li >>
the information, that “list of goods” is an attribute named «name», while «Goods» is
the text value of a tag
>>
li > «title» shout be written out as «columnTitle»
}
p > How to do that? Let's invent a simple definition language for that information:
Code ||
decl list(name);
decl title alias columnTitle;
||
p > Here you can ¬samples/list.yml2 download the complete list sample¬.
div id=bottom > ¬#top ^Top^¬ ¬programming >> Using YML 2¬ ¬index.en.yhtml2 (source)¬
}