S-Lang

The S-Lang programming library is a software library for Unix, Windows, VMS, OS/2, and Mac OS X. It provides routines for embedding an interpreter for the S-Lang scripting language, and components to facilitate the creation of text-based applications. The latter class of functions include routines for constructing and manipulating keymaps, an interactive line-editing facility, and both low and high-level screen/terminal management functions. It is distributed under the terms of the GNU General Public License.

The S-Lang programming library was started in 1992 by John E. Davis, considering that functions he wrote for a text editor might be useful in other programs. The earliest version of the library contained input/output routines for interacting with computer terminals and an implementation of a simple stack-based interpreter with a PostScript-like syntax that he developed for use in a scientific plotting program. The JED text-editor was the first program to both embed the interpreter and use the terminal I/O components of the library.

The interpreter makes up most of the S-Lang library, and is also where most of the development takes place. Although the original syntax supported by the interpreter resembled PostScript, the syntax has evolved to be much more C-like, with additional support for object-oriented style constructs. As a reflection of Davis's background in Physics and professional interest in scientific computing, the language natively supports many vectorized array-based operations similar to Matlab and IDL.

Until version 2.0, the interpreter was not a standalone program. Instead, Davis advocated embedding it into applications to make them extensible. Using the interpreter meant either embedding it in a C program, or using it in the context of another application (e.g., the JED editor). The S-Lang shell, slsh, was a demonstration program capable of little more than running scripts. Version 2.0, released in 2005, made slsh interactive, and it has evolved into an application in its own right, with a number of external modules for use by it. As such, it has become the S-Lang interpreter.

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