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 predicates. These declarations are used by the
load_foreign_resource/1, which performs the
actual binding of C functions to 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: