R中的Custom .Primitive函数

Question

I known *+* <- function(x,y){ x + y} in R.

But if I want to write a function like .print .

And I can show print(iris) with using iris.print .

How do I custom my function in R?

Answer 1

The simplest way is to use R's R3 classes.

A simple example. Assume we have a new data type --- a vector which we would like to print as a comma-separated string.

x <- c(1, 2, 3)
# Assign a class attribute. The first element is the class of the object;
# the second element is the parent class
class(x) <- c("Foo", "numeric")
# Define the print method
print.Foo <- function(x) {
  cat(paste(x, collapse = ", "), "\n")
}
# The method is called just like this
print(x)