Use delayed binding to create expensive functions

[hadley]

Because they're run once

Use for backports etc

[jimhester]

There isn't really enough detail here for me to be sure what you are talking about. But if it is delayedAssign() this is such a rarely needed technique I am not sure it is worth addressing in a general design document...

[hadley]

I was thinking specifically for packages, instead of initialising to NULL and then rebinding inside of .onLoad()

[hadley]

We now also have rlang::on_load(), so I no longer think we need this issue.