The R Project SVN R

% File src/library/methods/man/RMethodUtils.Rd

% Part of the R package, http://www.R-project.org

% Copyright 1995-2008 R Core Team

% Distributed under GPL 2 or later

\name{RMethodUtils}

%% FIXME:  undocumented utilities (Sep. 23/02)

\alias{asMethodDefinition}

\alias{standardGeneric-class}

\alias{standardGenericWithTrace-class}

\alias{nonstandardGeneric-class}

\alias{nonstandardGenericFunction-class}

\alias{nonstandardGroupGenericFunction-class}

\alias{OptionalFunction-class}

\alias{PossibleMethod-class}

\alias{optionalMethod-class}

\alias{derivedDefaultMethod-class}

%%

\alias{substituteFunctionArgs}

\alias{makeGeneric}

\alias{makeStandardGeneric}

\alias{generic.skeleton}

\alias{defaultDumpName}

\alias{doPrimitiveMethod}

\alias{conformMethod}

\alias{getGeneric}

\alias{getGroup}

\alias{getGroupMembers}

\alias{getMethodsMetaData}

\alias{assignMethodsMetaData}

\alias{matchSignature}

\alias{findUnique}

\alias{MethodAddCoerce}

\alias{.saveImage}

\alias{cacheMetaData}

\alias{cacheGenericsMetaData}

\alias{setPrimitiveMethods}

\alias{missingArg}

\alias{balanceMethodsList}

\alias{sigToEnv}

\alias{rematchDefinition}

\alias{unRematchDefinition}

\alias{addNextMethod,MethodDefinition-method}

\alias{addNextMethod,MethodWithNext-method}

\alias{addNextMethod}

\alias{.valueClassTest}

\alias{insertClassMethods}

%% Not for the user to know about!

\alias{.ShortPrimitiveSkeletons} %% used from C code

\alias{.EmptyPrimitiveSkeletons}

\title{Method Utilities}

\description{

  Utility functions to support the definition and use of formal

  methods.  Most of these functions will not normally be called directly

  by the user.

}

\usage{

getGeneric(f, mustFind=FALSE, where, package)

getGroup(fdef, recursive, where)

getGroupMembers(group, recursive = FALSE, character = TRUE)

getMethodsMetaData(f, where)

assignMethodsMetaData (f, value, fdef, where, deflt)

makeGeneric(f, fdef, fdefault =, group=list(), valueClass=character(),

            package =, signature = NULL, genericFunction = NULL,

            simpleInheritanceOnly = NULL)

makeStandardGeneric(f, fdef)

generic.skeleton(name, fdef, fdefault)

defaultDumpName(generic, signature)

doPrimitiveMethod(name, def, call= sys.call(sys.parent()),

                  ev = sys.frame(sys.parent(2)))

conformMethod(signature, mnames, fnames, f= , fdef, method)

matchSignature(signature, fun, where)

findUnique(what, message, where)

MethodAddCoerce(method, argName, thisClass, methodClass)

cacheMetaData(where, attach = TRUE, searchWhere = as.environment(where),

              doCheck = TRUE)

cacheGenericsMetaData(f, fdef, attach = TRUE, where, package, methods)

setPrimitiveMethods(f, fdef, code, generic, mlist)

missingArg(symbol, envir = parent.frame(), eval)

balanceMethodsList(mlist, args, check = TRUE)

sigToEnv(signature, generic)

rematchDefinition(definition, generic, mnames, fnames, signature)

unRematchDefinition(definition)

asMethodDefinition(def, signature, sealed = FALSE, fdef)

addNextMethod(method, f, mlist, optional, envir)

insertClassMethods(methods, Class, value, fieldNames, returnAll)

}

\section{Summary of Functions}{

  \describe{

    \item{\code{getGeneric}:}{

      returns the definition of the function named \code{f} as a generic.

      If no definition is found, throws an

      error or returns \code{NULL} according to the value of

      \code{mustFind}.  By default, searches in the top-level

      environment (normally the global environment, but adjusted to

      work correctly when package code is evaluated from the function

      \code{\link{library}}).

      Primitive functions are dealt with specially, since there is never

      a formal generic definition for them.  The value returned is the

      formal definition used for assigning methods to this primitive.

      Not all primitives can have methods; if this one can't, then

      \code{getGeneric} returns \code{NULL} or throws an error.

    }

    \item{\code{getGroup}:}{

      returns the groups to which this generic belongs, searching from

      environment \code{where} (the global environment normally by default).

      If \code{recursive=TRUE}, also all the group(s) of these groups.

    }

    \item{\code{getGroupMembers}:}{

      Return all the members of the group generic function named

      \code{group}.

      If \code{recursive} is \code{TRUE}, and some members are group

      generics, includes their members as well.

      If \code{character} is \code{TRUE}, returns just a character

      vector of the names; otherwise returns a list, whose elements may

      (or may not) include either names with a package attribute or

      actual generic functions.

      Note that members that are not defined as generic functions will

      \emph{not} be included in the returned value.  To see the raw data,

      use \code{getGeneric(group)@groupMembers}.

    }

    \item{\code{getMethodsMetaData},

      \code{assignMethodsMetaData},

      \code{mlistMetaName}:}{Utilities to get

      (\code{getMethodsMetaData}) and assign

      (\code{assignMethodsMetaData}) the metadata object recording the

      methods defined in a particular package, or to return the mangled

      name for that object  (\code{mlistMetaName}).

      The assign function should not be used directly.  The get

      function may be useful if you want explicitly only the outcome of

      the methods assigned in this package.  Otherwise, use

      \code{\link{getMethods}}.

    }

    \item{\code{matchSignature}:}{

      Matches the signature object (a partially or completely named

      subset of the signature arguments of the generic function object

      \code{fun}), and return a vector of all the classes in the order

      specified by \code{fun@signature}.  The classes not specified by

      \code{signature} will be \code{"ANY"} in the value, but extra

      trailing \code{"ANY"}'s are removed.  When the input signature is

      empty, the returned signature is a single \code{"ANY"} matching

      the first formal argument (so the returned value is always

      non-empty).

      Generates an error if any of the supplied signature names are

      not legal; that is, not in the signature slot of the generic

      function.

      If argument \code{where} is supplied, a warning will be issued

      if any of the classes does not have a formal definition visible

      from \code{where}.

    }

    \item{\code{MethodAddCoerce}:}{

      Possibly modify one or more methods to explicitly coerce this

      argument to \code{methodClass}, the class for which the method is

      explicitly defined.  Only modifies the method if an explicit

      coerce is required to coerce from \code{thisClass} to

      \code{methodClass}.

    }

    \item{\code{findUnique}:}{

      Return the list of environments (or equivalent) having an object named

      \code{what}, using environment \code{where} and its parent

      environments.  If more than one is found, a warning message is

      generated, using \code{message} to identify what was being

      searched for, unless \code{message} is the empty string.

    }

    \item{\code{cacheMetaData},

      \code{cacheGenericsMetaData},

      \code{setPrimitiveMethods}:}{

      Utilities for ensuring that the internal information about

      class and method definitions is up to date.  Should normally be

      called automatically whenever needed (for example, when a method

      or class definition changes, or when a package is attached or

      detached).  Required primarily because primitive functions are

      dispatched in C code, rather than by the official model.

      The \code{setPrimitiveMethods} function resets the caching

      information for a particular primitive function.  Don't call it

      directly.

    }

    \item{\code{missingArg}:}{

      Returns \code{TRUE} if the symbol supplied is missing \emph{from

        the call} corresponding to the environment supplied (by default,

      environment of the call to \code{missingArg}).  If \code{eval} is

      true, the argument is evaluated to get the name of the symbol to

      test.  Note that \code{missingArg} is closer to the

      \sQuote{Blue Book} sense of the \code{\link{missing}} function,

      not that of the current R base package implementation.  But beware

      that it works reliably only if no assignment has yet been made to

      the argument.  (For method dispatch this is fine, because

      computations are done at the beginning of the call.)

    }

    \item{\code{balanceMethodsList}:}{

      Called from \code{\link{setMethod}} to ensure that all nodes in

      the list have the same depth (i.e., the same number of levels of

      arguments).  Balance is needed to ensure that all necessary

      arguments are examined when inherited methods are being found and

      added to the \code{allMethods} slot.  No actual recomputation is

      needed usually except when a new method uses a longer signature

      than has appeared before.

      Balance requires that \emph{all} methods be added to the generic

      via \code{setMethod} (how else could you do it?) or by the initial

      \code{setGeneric} call converting the ordinary function.

    }

    \item{\code{sigToEnv}:}{

      Turn the signature (a named vector of classes) into an environment

      with the classes assigned to the names.  The environment is then

      suitable for calling \code{\link{MethodsListSelect}}, with

      \code{evalArgs=FALSE}, to select a method corresponding to the

      signature.  Usually not called directly: see

      \code{\link{selectMethod}}.

    }

    \item{\code{.saveImage}:}{

      Flag, used in dynamically initializing the methods package from

      \code{.onLoad}.

    }

    \item{\code{rematchDefinition},

      \code{unRematchDefinition}:}{

      If the specified method in a call to \code{\link{setMethod}}

      specializes the argument list (by replacing \dots), then

      \code{rematchDefinition} constructs the actual method stored.

      Using knowledge of how \code{rematchDefinition} works,

      \code{unRematchDefinition} reverses the procedure; if given a

      function or method definition that does not correspond to this

      form, it just returns its argument.

    }

    \item{\code{asMethodDefinition}:}{

      Turn a function definition into an object of class

      \code{\linkS4class{MethodDefinition}}, corresponding to the

      given \code{signature} (by default generates a default method

      with empty signature).  The definition is sealed according to

      the \code{sealed} argument.

    }

    \item{\code{addNextMethod}:}{

      A generic function that finds the next method for

      the signature of the method definition \code{method}  and caches

      that method in the method definition (promoting the class to

      \code{"MethodWithNext"}.  Note that argument \code{mlist} is

      obsolete and not used.

    }

    \item{\code{makeGeneric}:}{

      Makes a generic function object corresponding to the given

      function name, optional definition and optional default method.

      Other arguments supply optional elements for the slots of class

      \code{\linkS4class{genericFunction}}.

    }

    \item{\code{makeStandardGeneric}:}{

      a utility function that makes a valid function calling

      \code{standardGeneric} for name \code{f}.  Works (more or less)

      even if the actual definition, \code{fdef}, is not a proper

      function, that is, it's a primitive or internal.

    }

    \item{\code{conformMethod}:}{

      If the formal arguments, \code{mnames}, are not identical to the

      formal arguments to the function, \code{fnames},

      \code{conformMethod} determines whether the signature and the two

      sets of arguments conform, and returns the signature, possibly

      extended.  The function name, \code{f} is supplied for error

      messages. The generic function, \code{fdef}, supplies the

      generic signature  for matching purposes.

      The method assignment conforms if method and generic function have

      identical formal argument lists.  It can also conform if the

      method omits some of the formal arguments of the function but: (1)

      the non-omitted arguments are a subset of the function arguments,

      appearing in the same order; (2) there are no arguments to the

      method that are not arguments to the function; and (3) the omitted

      formal arguments do not appear as explicit classes in the

      signature.  A future extension hopes to test also that the

      omitted arguments are not assumed by being used as locally assigned

      names or function names in the body of the method.

    }

    \item{\code{defaultDumpName}:}{

      the default name to be used for dumping a method.

    }

    \item{\code{doPrimitiveMethod}:}{

      do a primitive call to builtin function \code{name} the definition

      and call provided, and carried out in the environment \code{ev}.

      A call to \code{doPrimitiveMethod} is used when the actual method

      is a .Primitive.  (Because primitives don't behave correctly as

      ordinary functions, not having either formal arguments nor a

      function body).

    }

  }

}

\seealso{\code{\link{setGeneric}}, \code{\link{setClass}},

  \code{\link{showMethods}}.

}

\examples{

getGroup("exp")

getGroup("==", recursive = TRUE)

getGroupMembers("Arith")

getGroupMembers("Math")

getGroupMembers("Ops") # -> its sub groups

}

\keyword{internal}