How to export a function from a package and access it only by specifying the namespace?

Peng Yu wrote:

Then I try the package 'try.package' in an R session. I'm wondering
why neither 'my_test_f' and 'try.package::my_test_f' work.

The error message you got below clearly explains this-- you did not export
my_test_f in your NAMESPACE file. ?To access unexported functions, you must
use the ':::' operator:

?try.package:::my_test_f()



Peng Yu wrote:

Why 'my_test_g' can be accessed with 'try.package::' and without
'try.package::'?

Because you exported it in the NAMESPACE file.



Peng Yu wrote:

Is there a way to make ?'my_test_g' accessible only by specifying the
namespace 'try.package::'?

No.

The purpose of the '::' operator is for those cases where multiple packages
are loaded that each export a function with the same name. ?This is known as
"masking" and the last loaded package will contribute the dominant
function-- i.e. the function the gets called when the user types
"functionName()" and not "packageName::functionName()". ?The "::" operator
allows the selection of functions that are masked by the dominant function.

If you really want to conceal a function from user-level code, don't export
it and it will only be accessible via the ":::" operator.

showMethods(where=getNamespace('try.package'))