The Advanced User's Guide

4 Working Beyond the Lisp Environment

The Foreign Function Interface allows you to load code that is written in computer languages other than Lisp into the Lisp environment, and it creates Lisp functions to call non-Lisp code. Similarly, you can write functions in this interface that convert information provided by Lisp functions to a format that can be used in a foreign environment.

The functionrun-program calls an executable program from Lisp. It can optionally redirect the standard input, standard output, and error output streams of the program to Lisp streams.

The manner in which the Foreign Function Interface operates is distinguished from the operations performed byrun-program in an important way:

• The Foreign Function Interface loads code into Lisp's address space. Thus, you can manipulate foreign data structures with the Foreign Function Interface.

• The functionrun-program starts up a program as a separate process. Thus, communication is limited to the standard input and standard output streams. Nonetheless,run-program is appropriate for many simple applications, such as invoking operating system services.

4.1 - The Foreign Function Interface

4.2 - Running UNIX programs from Lisp

4.3 - The C-to-FFI facility

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