The C# code from C# pragma foreign_proc declarations will be placed in the bodies of static member functions of an automatically-generated C# class. Since such C# code will become part of a static member function, it must not refer to the ‘this’ keyword. It may however refer to static member variables or static member functions declared with ‘pragma foreign_code’.
The input and output variables for a C# ‘pragma foreign_proc’ will have C# types corresponding to their Mercury types. The exact rules for mapping Mercury types to C# types are described in C# data passing conventions.
C# code in a
pragma foreign_proc declaration
for any procedure whose determinism indicates that it can fail
must assign a value of type ‘bool’ to the variable
‘SUCCESS_INDICATOR’. For example:
:- pred string.contains_char(string, character). :- mode string.contains_char(in, in) is semidet. :- pragma foreign_proc("C#", string.contains_char(Str::in, Ch::in), [will_not_call_mercury, promise_pure], "SUCCESS_INDICATOR = (Str.IndexOf(Ch) != -1);").
C# code for procedures whose determinism indicates that they cannot fail
should not access
Arguments whose mode is input will have their values set by the
Mercury implementation on entry to the C# code. If the procedure
succeeds, the C# code must set the values of all output arguments.
If the procedure fails, the C# code need only
SUCCESS_INDICATOR to false.