### Name: as
### Title: Force an Object to Belong to a Class
### Aliases: as as<- coerce coerce<- setAs coerce-methods
###   coerce,ANY,array-method coerce,ANY,call-method
###   coerce,ANY,character-method coerce,ANY,complex-method
###   coerce,ANY,environment-method coerce,ANY,expression-method
###   coerce,ANY,function-method coerce,ANY,integer-method
###   coerce,ANY,list-method coerce,ANY,logical-method
###   coerce,ANY,matrix-method coerce,ANY,name-method
###   coerce,ANY,numeric-method coerce,ANY,single-method
###   coerce,ANY,ts-method coerce,ANY,vector-method coerce,ANY,NULL-method
### Keywords: programming classes methods

### ** Examples

## using the definition of class "track" from Classes

## Don't show: 
setClass("track",
         representation(x="numeric", y="numeric"))
setClass("trackCurve",
         representation("track", smooth = "numeric"))
## End Don't show

setAs("track", "numeric", function(from) from@y)

t1 <- new("track", x=1:20, y=(1:20)^2)

as(t1, "numeric")

## The next example shows:
##  1. A virtual class to define setAs for several classes at once.
##  2. as() using inherited information

setClass("ca", representation(a = "character", id = "numeric"))

setClass("cb", representation(b = "character", id = "numeric"))

setClass("id")
setIs("ca", "id")
setIs("cb", "id")

setAs("id", "numeric", function(from) from@id)

CA <- new("ca", a = "A", id = 1)
CB <- new("cb", b = "B", id = 2)

setAs("cb", "ca", function(from, to )new(to, a=from@b, id = from@id))

as(CB, "numeric")

## Don't show: 
## should generate an error (should have been a function of one argument)
try(setAs("track", "numeric", function(x, y,z)x@y))
## End Don't show