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The S-Lang XPA Module Page


SLxpa binds the XPA library to the S-Lang language. It provides an importable module and associated .sl script which make XPA callable directly from S-Lang scripts.

XPA is a set of libraries (ANSI C, Tcl/Tk) and commandline tools, written at the Smithsonian Astrophysical Observatory, which provide a clean and simple IPC (inter-process communication) mechanism that is also surprisingly powerful. It can be used to build loosely-coupled client/server programs that interact either on a single machine or across local and wide-area networks; we have also found it useful for automated regression testing, especially for GUIs that are traditionally difficult to test in this manner. The XPA library provides much of the functionality of more well-known mechanisms like CORBA, Java RMI, and the now-defunct ToolTalk, but is much smaller and, we feel, can be easier to learn, embed, deploy, and utilize.

The S-Lang interpreter is part of the widely-used, open-source library of the same name, and provides a scripting environment well-suited for scientific and engineering tasks, due to the powerful, compact, fast, and robust multidimensional numerical capabilities that are native to the language.

SLxpa also bundles the DS9 package, which provides a number of functions to streamline interactions with the SAOds9 image display and analysis tool widely used in astronomy, and includes a WCS editor GUI. By augmenting the numerical strength and modular extensibility of the S-Lang platform with the imaging capabilities of SAOds9, the DS9 script can make a powerful addition to your image analysis toolset.

This page was last updated Jul 31, 2010 by Michael S. Noble. To comment on it or the material presented here, send email to
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