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1. Preface

S-Lang is an interpreted language that was designed from the start to be easily embedded into a program to provide it with a powerful extension language. Examples of programs that use S-Lang as an extension language include the jed text editor, the slrn newsreader, and sldxe (unreleased), a numerical computation program. For this reason, S-Lang does not exist as a separate application and many of the examples in this document are presented in the context of one of the above applications.

S-Lang is also a programmer's library that permits a programmer to develop sophisticated platform-independent software. In addition to providing the S-Lang extension language, the library provides facilities for screen management, keymaps, low-level terminal I/O, etc. However, this document is concerned only with the extension language and does not address these other features of the S-Lang library. For information about the other components of the library, the reader is referred to the The S-Lang Library Reference.

1.1 A Brief History of S-Lang

I first began working on S-Lang sometime during the fall of 1992. At that time I was writing a text editor (jed), which I wanted to endow with a macro language. It occured to me that an application-independent language that could be embedded into the editor would prove more useful because I could envision embedding it into other programs. As a result, S-Lang was born.

S-Lang was originally a stack language that supported a postscript-like syntax. For that reason, I named it S-Lang, where the S was supposed to emphasize its stack-based nature. About a year later, I began to work on a preparser that would allow one to write using a more traditional infix syntax making it easier to use for those unfamiliar with stack based languages. Currently, the syntax of the language resembles C, nevertheless some postscript-like features still remain, e.g., the `%' character is still used as a comment delimiter.

1.2 Acknowledgements

Since I first released S-Lang, I have received a lot feedback about the library and the language from many people. This has given me the opportunity and pleasure to interact with several people to make the library portable and easy to use. In particular, I would like to thank the following individuals:

Luchesar Ionkov <> for his comments and criticisms of the syntax of the language. He was the person who made me realize that the low-level byte-code engine should be totally type-independent. He also improved the tokenizer and preparser and impressed upon me that the language needed a grammar.

Mark Olesen <> for his many patches to various aspects of the library and his support on AIX. He also contributed a lot to the pre-processing (SLprep) routines.

John Burnell <> for the OS/2 port of the video and keyboard routines. He also made value suggestions regarding the interpreter interface.

Darrel Hankerson <> for cleaning up and unifying some of the code and the makefiles.

Dominik Wujastyk <> who was always willing to test new releases of the library.

Michael Elkins <> for his work on the curses emulation.

Ulli Horlacher <> and Oezguer Kesim <> for the S-Lang newsgroup and mailing list.

Hunter Goatley, Andy Harper <>, and Martin P.J. Zinser <> for their VMS support.

I am also grateful to many other people who send in bug-reports and bug-fixes, for without such community involvement, S-Lang would not be as well-tested and stable as it is. Finally, I would like to thank my wife for her support and understanding while I spent long weekend hours developing the library.

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