Node:Object Declaration, Next:Method Declarations, Previous:Obj Declared Objects, Up:Obj Declared Objects
An object object-identifier is declared by writing it in the
following form:
object-identifier :: {
sentence-1 &
sentence-2 &
:
sentence-n
}.
where object-identifier is a Prolog term that is either an
atom or a compound term of the form functor(V1,...,Vn), where
V1,...,Vn are distinct variables. The object body consists of a number
of sentences, possibly none, surrounded by braces, where each sentence
is either a method-directive, to be executed when the object is created,
or a method-clause. A method is a number of method-clauses with
the same principal functor. A method-clause has a clausal syntax similar to
that of Prolog, but instead of usual predicate calls in the body of a clause
there are method-calls. Ordinary Prolog goals are also allowed in a
prefixed form, using : as a prefix. A method-directive is a directive which
contains method-calls.
All sentences are subject to term expansion (see Definite, built-in
expand_term/2) before further processing, so in particular
definite clause grammar syntax can be used in method-clauses. In
addition, before expand_term/2, sentences are expanded by the
predicate user:method_expansion/3.
method_expansion(+Term1,+ObjectIdentifier,?Term2) [Hook]
user:method_expansion(+Term1,+ObjectIdentifier,?Term2)
Defines transformations on methods
similarly as user:term_expansion/[2,4]. At the end of an object
definition, user:method_expansion/3 is called with
end_of_object.