The functorial interface

TyXML provides a functorial interface to implement HTML and SVG on top of any XML implementations. This is used heavily by Eliom to implement the F and D modules, providing respectivelly a functionnal and a DOM version of the HTML implementation.

The Make functors

Those interfaces are available in the modules Html5_f and Svg_f. They provide a functor Make which takes a concrete implementation of Xml following Xml_sigs.​T. A default implementation is provided by the Xml module. The functor Html5_f.​Make also needs an Svg implementation that you can obtain, for example, with the functor Svg_f.​Make. Due to typing constraints (see next section), The Xml implementation will always need to provide a wrap type answering this definition:

type 'a wrap = 'a

Wrapping up the nodes

Beside the #Make functor. those two modules provide a MakeWrapped functor, which allows to wrap Xml elements in a monad. A good example of application is the R modules with reactive nodes in eliom. Here is the simplified signature of the div element:

R.div : 'a elt list signal -> div elt

signal will wrap the input of every Xml nodes and be integrated in the resulting node.

In order to do this, You need to provide an additional Wrap module to the functor, following the signature Xml_wrap.​T. This implements operations over the type of nodes along with a special type for lists of nodes. The Xml implementation follow Xml_sigs.​Wrapped, which is the same as Xml_sigs.​T, but with arbitrary 'a wrap type.

An identity wrapper, Xml_wrap.​NoWrap, is provided. The Make functor is only MakeWrapped partially applied to NoWrap.