Operators

Operators

This is a brief note about the use of two operators within the RS package.

@ - Slot Operator

The @ operator is used in R to access slots in S4 and S7 classes.

I decided to use this operator in RS because the $ is so pervasive in R code, and I wanted an operator that would help the user identify that the object on the left-hand side is an RS class, rather than a list, R6 class, environment, dataframe, etc.

For example, when I see:

x$y <- 1

it’s a little ambiguous what x is.

However, when you see:

x@y <- 1

x can only be an RS class, or an S4/S7 class if that is also in your project.

I hope this makes reading the code a bit easier.

:= - Attribute Assignment Operator

The := is used when defining a class’ attributes.

For example:

Class(
    "Foo",

    a := t_int,
    x := t_cplx
)

a is assigned the t_int type, while x is assigned the t_cplx type.

Like the @ operator, I primarily did this for readability (i.e. to differentiate from a common assignment like x = 1), however, it also allows me to add futher assignment features in the future.