# Double dispatch in R: S4 vs vctrs

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Why do we may need double dispatch? In most cases, when writing R scripts or even creating R packages, it is enough to use standard functions or S3 methods. However, there is one important field that forces us to consider double dispatch question: arithmetic operators.
Suppose we’d like to create a class, which fits the problem we’re currently working on. Let’s name such class beer.
beer <- function(type){ structure(list(type = type),class = "beer") } opener <- function(){ structure(list(), class = "opener") } pilsner <- beer("pilnser") my_opener <- opener() Then, we create an operator which defines some non-standard behaviour.
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