associated_surface
EXPRESS specification:
FUNCTION
associated_surface
(arg : pcurve_or_surface) : surface;
LOCAL
surf : surface;
END_LOCAL;
IF 'STRUCTURAL_FRAME_SCHEMA.PCURVE' IN TYPEOF(arg) THEN
surf := arg.basis_surface;
ELSE
surf := arg;
END_IF;
RETURN(surf);
END_FUNCTION
;