Calls to external functions

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Calls to external functions

Edges in graphs may be simulated by calling external C functions. The name of the functions must appear in a DECLARE declaration:

$\begin{verbsyntax}\synrule{ExternalFunctionDeclaration}{IdentKommaList ':' 'fun'... ...aration}{IdentKommaList ':' 'proc' NodeType '->' SetOrNodeType} \end{verbsyntax}$

The first alternative declares an external C function returning a node type or a set over a node type. The second alternative declares a void C procedure with two parameters, the first an input parameter (pointer/object type), the second one an output set parameter (set type). Examples of declarations:

$\begin{examplefoot}DECLARE f1: fun file -> file; f2, f3: fun file -> conslist... ...); p1: proc file -> file; p2,p3: proc file -> consset(file); \end{examplefoot}$

f1 - p3 may all be refered to as binary predicate names in rule tests:

$\begin{examplefoot}( f1(O1,O2), p3(O2,O3) ==> a_normal_graph_edge(O1, O3) ) \end{examplefoot}$

The semantics of external C function calls in rule transformations is not defined.

Uwe Assmann
1998-12-22