[R] Operator overloading

[Peter Dalgaard]

Tine wrote:
> Hi!
>
> I was just wondering is there anyway to overload operator for custom
> class.
> For example:
> I have two matrices A and B with same dimensions. I want to overload
> operator '+' with my own function.
> Or even better can I create my own (new) operator.
> Example:
> A+-B where '+-' would be some function.
>
You can define an S3 method

"+.myclass" <- function(a,b) {...}

Notice that dispatch is only on the 1st argument. This is a generic
weakness of  S3 methods. The Matrix package implements similar things
with S4 methods, but it does tend to get rather complicated.

There's a general method for user defined binary operators using
functions with names of the form %any% (see ?Syntax):

> "%_%" <- function(a,b) paste(a,b,sep="")
> "Hello," %_% " " %_% "world"
[1] "Hello, world"



> bye,
>  Tine
>
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