Class MethodsList, Representation of Methods for a Generic Function

Description

Objects from this class are generated and revised by the definition of methods for a generic function.

Details

Suppose a function f has formal arguments x and y. The methods list object for that function has the object as.name("x") as its argument slot. An element of the methods named "track" is selected if the actual argument corresponding to x is an object of class "track". If there is such an element, it can generally be either a function or another methods list object.

In the first case, the function defines the method to use for any call in which x is of class "track". In the second case, the new methods list object defines the available methods depending on the remaining formal arguments, in this example, y.

Each method corresponds conceptually to a signature; that is a named list of classes, with names corresponding to some or all of the formal arguments. In the previous example, if selecting class "track" for x, finding that the selection was another methods list and then selecting class "numeric" for y would produce a method associated with the signature x = "track", y = "numeric".

You can see the methods arranged by signature by calling the function showMethods, A methods list can be converted into an ordinary list with the methods arranged this way (in two different forms) by calling the functions listFromMlist and linearizeMlist.

Slots

argument:

Object of class "name". The name of the argument being used for dispatch at this level.

methods:

A named list of the methods (and method lists) defined explicitly for this argument. The names are the names of classes, and the corresponding element defines the method or methods to be used if the corresponding argument has that class. See the details below.

allMethods:

A named list, contains all the directly defined methods from the methods slot, plus any inherited methods. Ignored when methods tables are used for dispatch (see Methods

Extends

Class "OptionalMethods", directly.