Accepts a function
fn and returns a function that guards invocation of
fn such that
fn can only ever be called once, no matter how many times
the returned function is invoked. The first value calculated is returned in
var addOneOnce = R.once(x => x + 1); addOneOnce(10); //=> 11 addOneOnce(addOneOnce(50)); //=> 11
The function to wrap in a call-only-once wrapper.
The wrapped function.