SICStus Prolog

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Mixing C and Prolog

SICStus Prolog provides a bi-directional, procedural interface for program parts written in C and Prolog. The C side of the interface defines a number of functions and macros for various operations. On the Prolog side, you have to supply declarations specifying the names and argument/value types of C functions being called as Prolog predicates. These declarations are used by the predicate load_foreign_resource/1, which performs the actual binding of C functions to Prolog predicates.

In most cases, the argument/value type declaration suffice for making the necessary conversions of data automatically as they are passed between C and Prolog. However, it is possible to declare the type of an argument to be a Prolog term, in which case the receiving function will see it as a "handle" object, called an SP_term_ref, for which access functions are provided.

The C support routines are available in a development system as well as in runtime systems. The support routines include:

Static and dynamic linking of C code into the Prolog environment.
Automatic conversion between Prolog terms and C data with foreign/[2,3] declarations.
Functions for accessing and creating Prolog terms, and for creating and manipulating SP_term_refs.
The Prolog system may call C predicates which may call Prolog back without limits on recursion. Predicates that call C may be defined dynamically from C.
Support for creating stand-alone executables.
Support for creating user defined Prolog streams.
Functions to read and write on Prolog streams from C.
Functions to install interrupt handlers that can safely call Prolog.
Functions for manipulating mutual exclusion locks.
User hooks that can be used to perform user defined actions on a number of occasions e.g. before reading a character from the standard input stream, upon reinitialization, etc.