Struct Embedding in R Programming Language
R supports creating custom data structures using lists and environments, which can be used to simulate struct-like behavior. We’ll use this approach to demonstrate a similar concept to struct embedding.
# Create a base "struct"
base <- function(num) {
self <- list(num = num)
self$describe <- function() {
sprintf("base with num=%d", self$num)
}
class(self) <- "base"
return(self)
}
# Create a container "struct" that embeds base
container <- function(num, str) {
self <- list(
base = base(num),
str = str
)
# Add methods from base to container
self$describe <- self$base$describe
class(self) <- c("container", "base")
return(self)
}
# Main function to demonstrate usage
main <- function() {
# Create a container instance
co <- container(1, "some name")
# Access fields directly
cat(sprintf("co={num: %d, str: %s}\n", co$base$num, co$str))
# Access through the full path
cat("also num:", co$base$num, "\n")
# Call the describe method
cat("describe:", co$describe(), "\n")
# Demonstrate interface-like behavior
describer <- function(obj) {
UseMethod("describer")
}
describer.container <- function(obj) {
obj$describe()
}
cat("describer:", describer(co), "\n")
}
# Run the main function
main()
In this R code:
We define
base
andcontainer
as functions that return lists with attached methods, simulating struct-like behavior.The
container
function includes abase
instance, similar to embedding in the original example.We use the
$
operator to access fields and methods, which is similar to the dot notation in many other languages.To simulate interface-like behavior, we use R’s S3 method dispatch system with
UseMethod
and method definitions for specific classes.The
main
function demonstrates creating and using these struct-like objects.
When you run this script, you should see output similar to:
co={num: 1, str: some name}
also num: 1
describe: base with num=1
describer: base with num=1
This R code demonstrates concepts similar to struct embedding, showing how to create composite data structures and share behavior between them. While R doesn’t have built-in support for structs or interfaces, we can use its flexible list and environment systems to achieve similar functionality.