MysterX: A Scheme Toolkit for Building Interactive Applications with COM

MysterX is an object-oriented Scheme toolkit for building applications from oo-the-shelf COM components. While the COM support in languages such as Haskell and Mercury requires the use of an interface compiler to generate stub code, MysterX uses the reeective capabilities of OLE Automation to make value-marshalling decisions at run-time. MysterX hosts COM components in windows that display Dynamic HTML, without requiring a separate browser. Scheme code can manipulate HTML elements and their style properties in such windows to create interesting visual eeects. Event handlers written in Scheme can be associated with HTML elements and COM objects. By integrating these diverse technologies , MysterX can be used to write complete GUI applications. MysterX is an object-oriented Scheme toolkit for building interactive applications with components that adhere to the Component Object Model (COM). COM allows applications to be built from oo-the-shelf components. Components and their host programs can be written in any language; a component and its host program may be written in different languages. Most often, COM components are contained in applications built with Microsoft's Visual Basic or with various implementations of C++. Another way of using COM components is to \script" them in Web pages containing code in either JavaScript or VBScript, a browser-hosted version of Visual Basic. Unfortunately, these usual approaches of handling COM components rely on languages that make the task somewhat cumbersome. To overcome this problem, several research groups have developed COM support for languages with clean syntax, structure, and semantics. MysterX, Rice's eeort at adding COM support for Scheme, uses Scheme to particular advantage. By combining other technologies with COM, MysterX is able to use COM components in dynamic, interactive applications. A COM component instance is an object with state; most components have some visual representation. Displayable COM objects are ordinarily hosted in a container, such as a Web browser. In MysterX, COM components are hosted in a window containing Dynamic HTML, though no Web browser is run directly. Therefore,