2.13.1 How MathLink Is Used

Most of this book has been concerned with how human users interact with Mathematica. MathLink provides a mechanism through which programs rather than human users can interact with Mathematica.

• Calling functions in an external program from within Mathematica.

• Calling Mathematica from within an external program.

• Setting up alternative front ends to Mathematica.

• Exchanging data between Mathematica and external programs.

• Exchanging data between concurrent Mathematica processes.

MathLink provides a general interface for external programs to communicate with Mathematica. Many standard software systems now have MathLink compatibility either built in or available in add-on modules.

In addition, the MathLink Developer Kit bundled with most versions of Mathematica provides the tools you need to create your own MathLink-compatible programs.

Once you have a MathLink-compatible program, you can transparently establish a link between it and Mathematica.

The link can either be on a single computer, or it can be over a network, potentially with a different type of computer at each end.

• Implementing inner loops in a low-level language.

• Handling large volumes of data external to Mathematica.

• Sending Mathematica graphics or other data for special processing.

• Connecting to a system with an existing user interface.

MathLink-compatible programs range from very simple to very complex. A minimal MathLink-compatible program is just a few lines long. But it is also possible to build very large and sophisticated MathLink-compatible programs. Indeed, the Mathematica notebook front end is one example of a sophisticated MathLink-compatible program.

• MathLink is a mechanism for exchanging Mathematica expressions between programs.

Much of the power of MathLink comes from its use of Mathematica expressions. The basic idea is that MathLink provides a way to exchange Mathematica expressions between programs, and such expressions can represent absolutely any kind of data.

• An array of numbers.

• A collection of geometrical objects.

• A sequence of commands.

• A stream of text.

• Records in a database.

• The cells of a Mathematica notebook.

The MathLink library consists of a collection of routines that allow external programs to send and receive Mathematica expressions.

The MathLink Developer Kit provides utilities for incorporating these routines into external programs. Utilities are included for a variety of languages, although in this chapter we discuss mainly the case of C.

An important feature of the MathLink library is that it is completely platform independent: it can transparently use any interprogram communication mechanism that exists on your computer system.