12.1 Overview of the Interface

A special include file called SWI-Prolog.h should be included with each C source file that is to be loaded via the foreign interface. The installation process installs this file in the directory include in the SWI-Prolog home directory (?- current_prolog_flag(home, Home).). This C header file defines various data types, macros and functions that can be used to communicate with SWI-Prolog. Functions and macros can be divided into the following categories:

• Analysing Prolog terms
• Constructing new terms
• Unifying terms
• Returning control information to Prolog
• Registering foreign predicates with Prolog
• Calling Prolog from C
• Recorded database interactions
• Global actions on Prolog (halt, break, abort, etc.)