ClassNameOrExpression-class

This class is used to represent a type test that is specified either
 as a collection of class names (and whether to check for strict
 equality or inheritance) or a dynamic predicate expression that is
 evaluated at run-time to determine whether the test is satisfied. We may not need this in the "new" class hierarchy. It was created
 originally to be a union of character vectors, <code>call</code>s or
 <code>expression</code>s. But now that we have <code>NamedTypeTest</code> and
 <code>DynamicTypeTest</code>, we could perhaps use a common base class.

classes

A prototype for a mechanism for specifying the types of
parameters and the return value for an R function. This is
meta-information that can be used to generate stubs for servers
and various interfaces to these functions. Additionally, the
arguments in a call to a typed function can be validated using
the type specifications.
We allow types to be specified as either
i) by class name using either inheritance -  is(x, className),
or strict instance of - class(x) %in% className, or
ii) a dynamic test given as an R expression which is evaluated
at run-time.
More precise information and interesting tests can be done via
ii), but it is harder to use this information as meta-data as
it requires more effort to interpret it and it is of course
run-time information. It is typically more meaningful.

Duncan Lang

TypeInfo

Optional Type Specification Prototype

ClassNameOrExpression-class function

 A virtual Class: No objects may be created from it. 

Objects from the Class

 No methods defined with class "ClassNameOrExpression" in the
  signature. 

Methods

This class is used to represent a type test that is specified either
 as a collection of class names (and whether to check for strict
 equality or inheritance) or a dynamic predicate expression that is
 evaluated at run-time to determine whether the test is satisfied.

 We may not need this in the "new" class hierarchy. It was created
 originally to be a union of character vectors, <code>call</code>s or
 <code>expression</code>s. But now that we have <code>NamedTypeTest</code> and
 <code>DynamicTypeTest</code>, we could perhaps use a common base class.

ClassNameOrExpression-class: Class "ClassNameOrExpression" to represent type information as either class names or arbitrary language test

Description

Arguments

Objects from the Class

Methods

See Also