Language Reference/Attributes
Template:Preliminary Documentation
Various definitions and declarations can be annotated with attributes. This section describes the general syntax of attributes and where they can be placed. It also describes the meaning of the specific attributes.
Syntax
Attributes : [ Attribute-comma-sep-list ]
Attribute : one of LowerCaseIdentifier LowerCaseIdentifier ( Literal-comma-sep-list )
Where the literals must either be numbers or string literals.
Insertion Points
The attributes of interfaces, classes and implementations are right before the scope qualifications.
InterfaceDeclaration : interface IinterfaceName Attributes-opt ScopeQualifications Sections end interface IinterfaceName-opt
ClassDeclaration : class ClassName ConstructionType-opt Attributes-opt ScopeQualifications Sections end class ClassName-opt
ClassImplementation : implement ClassName Attributes-opt ScopeQualifications Sections end implement ClassName-opt
The attributes of constants, domains, predicates, properties and facts is at the end (i.e. right before the terminating dot).
ConstantDefinition: one of ConstantName = ConstantValue Attributes-opt ConstantName : TypeName = ConstantValue Attributes-opt
DomainDefinition: DomainName FormalTypeParameterList-opt = TypeExpression Attributes-opt
PredicateDeclaration : PredicateName : PredicateDomain LinkName-opt Attributes-opt PredicateName : PredicateDomainName LinkName-opt Attributes-opt
PropertyDeclaration : PropertyName : PropertyType FlowPattern-list-opt Attributes-opt
FactDeclaration : FactVariableDeclaration Attributes-opt FactFunctorDeclaration Attributes-opt
The attributes of formal arguments are at the end.
FormalArgument : TypeExpression ArgumentName-opt Attributes-opt
Specific Attributes
byVal
An argument is transferred directly on the stack rather than using a pointer. Valid for formal predicate arguments provided the language is stdcall, apicall or c.
predicates externalP : (point Point [byVal]) language apicall.
deprecated
The declared entity is deprecated. The string literal describes how to migrate from it. The entity still exist, but usage will cause a warning. The entity will not exist in future versions of Visual Prolog. Valid for member declarations and scopes.
predicates oldFasioned : (string Arg) [deprecated("Use newFasion instead")].
formatString
The argument is a format string for a subsequent ellipsis argument (i.e. ...). Valid for one string argument of a predicate with an ellipsis argument. The use of formatString will make the compiler check the validity of actual arguments with respect to actual format strings (where possible).
predicates writef : (string Format [formatString], ...).
in
The argument is an input argument. Valid for a formal predicate argument.
predicates pred : (string InputArg [in]).
inline
inline alters the memory layout of a struct (i.e. a single alternative functor domain with an align qualification). The corresponding field is inlined instead of being pointed to.
domains point = align 4 p(integer X, integer Y). domains rectangle = align 4 r( point UpperLeft [inline], point LowerRight [inline] ).
It is also possible to inline fixed size string and string8 fields in structs:
domains device = align 4 device( integer Id, string DeviceName [inline(32)] ).
noDefaultConstructor
Used for a class to indicate that it should not have an implicit default constructor, and can thus be used to a class that does not have any constructors at all. Valid for an object creating class declaration.
class classWithoutPublicConstructors : myInterface [noDefaultConstructor] ... end class classWithoutPublicConstructors
out
The argument is an output argument. Valid for a formal predicate argument.
predicates pred : (string OutputArg [out]).
retired
The declared entity is retired. The string literal describes how to migrate from it. The entity does not exist anymore.
predicates veryOldFasioned : (string Arg) [retired("Use newFasion instead")].
union
Used for creating functor domains with several alternatives but no real functors. This should only be used to mimic C/C++ union structs in low-level interfacing. Valid for functor domain with several alternatives and alignment.
domains u64var = align 4 u64(unsigned64 Value64); u64_struct(unsigned Low32, unsigned High32) [union].
used
An unused local member can be marked used to prevent the compiler to issue a warning and remove the corresponding code. Valid for local members.
predicates seeminglyUnused : () [used].