Question on Code snippet semantics

I came across this code in library.R

package <- as.character(substitute(package))

where package is the first argument to the "library" function.

I've been racking my brains to understand why this is not just an elaborate (and ineffcient) way to write:

package <- "package"

E.g.

package <- as.character(substitute(package))
package

[1] "package"

Thanks
Mick Jordan

Frequently used in a function body, where the function author wants the argument to be passed as an object name, rather than a character vector, or perhaps both, as is the case with library() and require().

For example:

test <- function(x) {as.character(substitute(x))}

# Quoted, passing "MyPackage" as a character vector

test("MyPackage")

[1] "MyPackage"


# Not quoted, passing the object MyPackage

test(MyPackage)

[1] "MyPackage"


In both cases, the argument passed as 'x' can then be used within the function as a character vector, rather than as the object itself.

Regards,

Marc Schwartz