Language Reference/Attributes

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 is right before the scope qualifications.

InterfaceDeclaration :
   interface IinterfaceName Attributes ScopeQualifications Sections end interface IinterfaceName-opt

ClassDeclaration :
   class ClassName ConstructionType-opt Attributes ScopeQualifications Sections end class ClassName-opt

ClassImplementation :
   implement ClassName Attributes 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
    ConstantName : TypeName = ConstantValue Attributes

DomainDefinition:
    DomainName FormalTypeParameterList-opt = TypeExpression Attributes

PredicateDeclaration :
   PredicateName : PredicateDomain LinkName-opt Attributes
   PredicateName : PredicateDomainName LinkName-opt Attributes

PropertyDeclaration :
    PropertyName : PropertyType FlowPattern-list-opt Attributes

FactDeclaration :
   FactVariableDeclaration Attributes
   FactFunctorDeclaration Attributes

The attributes of formal arguments is at the end.

FormalArgument :
    TypeExpression ArgumentName-opt Attributes

Specific Attributes

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.

Example

predicates
    oldFasioned : (string Arg) [deprecated("Use newFasion instead")].

retired

The declared entity is retired the string literal describes how to migrate from it. The entity does not exist anymore.

Example

predicates
    veryOldFasioned : (string Arg) [retired("Use newFasion instead")].

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.

Example

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:

Example

domains
    device = align 4
        device(
            integer Id,
            string DeviceName [inline(32)]
        ).