Hi, 
 
This works fine.
>setClass("a",representation(b="list",c="list"))
>new("a",b=list(7))
>An object of class "a"
Slot "b":
[[1]]
[1] 7
 

Slot "c":
list()
 
But, now suppose you want a slot to accept an object of class formula...
>setClass("a",representation(b="list",c="formula"))
>new("a",b=list(7))
>Error in validObject(.Object) : invalid class "a" object: invalid object
for slot "c" in class "a": got class "NULL", should be or extend class
"formula"
 
Why can't new handle this? Why must the slot be defined? 
 
If I call new without any named arguments, it works fine
> new("a")
An object of class "a"
Slot "b":
list()
 
Slot "c":
NULL
 
If I call new with only a formula, it works fine.
> new("a",c=formula(x~y))
An object of class "a"
Slot "b":
list()
 
Slot "c":
x ~ y
 
How can I get R to do this?
>setClass("a",representation(b="list",c="formula"))
>new("a",b=list(7))
An object of class "a"
Slot "b":
[[1]]
[1] 7 
 
Slot "c":
NULL
 
Thanks, 
Steve
 
platform i386-pc-mingw32
arch     i386           
os       mingw32        
system   i386, mingw32  
status                  
major    2              
minor    1.1            
year     2005           
month    06             
day      20             
language R 

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