The type<-check
method is the normal way to activate a type. The first argument is the
object to be checked. The second is the receiver that requests the
conversion. The latter is currently used only for the
type<->kind
member.
Types are normally referred to by their type<-name
rather than by their reference. For this reason type checking and
conversion is also accessible through pce<-convert.
The following two lines are identical:
?- get(@pce, convert, '34', int, Int).
?- get(type(int), check, '34', Int).
First, type->validate
is activated. If this fails, type<-translate
is activated and the result thereof is returned.
- See also
- - class function
- pce<-convert
- text_item-type
- type->validate
- type<-translate
- type-supers
Convert a name into a type. This is the normal way to define or use a
type. The conversion syntax is (informally) defined below:
<Type> ::= <KindType>
| <SingleType> '...' % Methods: Varargs
<KindType> ::= 'alien:'<C-type> % Alien (C) types
| 'member:'<Single> % Members
<Single> ::= <PrimType>
| <Single>'|'<Single> % Disjunction
| '['Single']' % May be @default
| <Single>'*' % May be @nil
<PrimType> ::= <PredefinedType> % any defined type
| {<Name>',' ...} % name_of
| <int>'..'<int> % integer range
| <real>'..'<real> % real range
| <ClassName>
Below are some examples:
point Instance of class point or a subclass
int integer
[name] A name or @default
graphical* A graphical object or @nil
int|point integer or point
{left,right} either the name 'left' or 'right'
- .100 integer in the range 0 ... 100 (including) name
|function
Accepts a name or a function
object.
- See also
- - !bad_type_syntax
- pce<-convert
- type->initialise
Create a copy of a type with a new name. This may be used to create
synonym types or extend types in ways not supported by the default
conversion from a name to a type. Example:
?- get(@pce, convert, '{left,center,right}', type, X),
?- get(X, copy, format_name, _).
Creates a type format_name that accepts the names’left’,’center’or’right’.
- See also
- type
->initialise
Convert the first argument into a datum that satisfies the type. The
second argument is optional context information. Both variables and
methods pass the receiver through this argument. The pseudo code of this
method is:
translate(Type type, Any value, Object context)
{ Activate translate_function.
IF successful, return the translated value;
ELSE try super-types until one succeeds and return the value
}
NOTE: Normally not activated directly,
but through
type<-check
because the argument may not be of the requested type.
- See also
- - type
->validate
- type<-check
- type-translate_function
Chain with values that satisfy the type
object. This method is exploited by text_item<-completions
to perform automatic completion.
Currently this method takes care of:
