R help - Sep 2008 - Derived classes

Coming from a C++ and C# background I would like to know how inheritance works
with 'R'. The classical example is I can define an abstract class
'Shape' and have an array of 'Shape's but each instance could be
a Circle, Square, Triangle, etc. because they all derive from 'Shape'.
At runtime if I wish I can tell the type of the 'Shape' using various
language specific operators. In 'R' it seems that each
'function' in general returns an object that is specific to that
function. For example 'stl' returns an 'stl' object,
'lm' retuirns an 'lm' object, 'kmeans' returns a
'kmens' object etc. If I have an array of these objects what can I use
to tell the type of object in 'R' and runtime? Any examples would be
helpful.

Thank you.

Kevin

Try this:

# constructor for Square
makeSquare <- function(name, side) structure(list(name = name, side side),
class = c("Square", "Shape"))

# generic
getName <- function(shape) UseMethod("getName")
# Shape method
getName.Shape <- function(shape) shape$name

# generic
getArea <- function(shape) UseMethod("getArea")
# Square method
getArea.Square <- function(shape) shape$side ^ 2

sq <- makeSquare("a", 10)
getName(sq)  # inherits getName method from Shape class
getArea(sq) # uses getArea method for Square class

On Thu, Sep 4, 2008 at 11:56 PM,  <rkevinburton at charter.net>
wrote:
> Coming from a C++ and C# background I would like to know how inheritance
works with 'R'. The classical example is I can define an abstract class
'Shape' and have an array of 'Shape's but each instance could be
a Circle, Square, Triangle, etc. because they all derive from 'Shape'.
At runtime if I wish I can tell the type of the 'Shape' using various
language specific operators. In 'R' it seems that each
'function' in general returns an object that is specific to that
function. For example 'stl' returns an 'stl' object,
'lm' retuirns an 'lm' object, 'kmeans' returns a
'kmens' object etc. If I have an array of these objects what can I use
to tell the type of object in 'R' and runtime? Any examples would be
helpful.
>
> Thank you.
>
> Kevin
>
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