print text when calling a model - r

Question

I hope this is not a double post. I've been looking for an answer.
I have a function that returns a rather big list. So i would like it to print some text in between all the results of the list. A bit as you know it from lm and other models.
Consider this R script
y<-function(z)
{
l<-list()
print("hello world")
l$answer<-2*z
return(l)
}
x<-y(5)
This is a small example. I tried a solution with print but this is a bad solution , simply because it executes print when i save the variable as x<-fun(5). I just want it to execute text when you ask it explicit, or even better,if you can construct your own "summary" command to a list.
Thanks for your time.

Answer 1

If I understood what you want to do , I think you are looking to implement the S3method print.
set the class attribute :"someclass" of the y function return value
define print.someclass
here the code:
y<-function(z)
{
l<-list()
l$answer<-2*z
## Roland comment : usually better to preserve existing classes:
class(l) <- c('someclass', class(l))
return(l)
}
print.someclass<-
function(x,...){ ## add here what you want to print
print("hello world")
}
x<-y(5)
Now when you type x at console or print(x):
x
[1] "hello world"