Creates a reactive page. A reactive page is defined by a function that is called once the participant reaches a given location in the timeline. This function must be idempotent, i.e. calling it multiple times should have the same effect as calling it once).

reactive_page(fun, next_elt = TRUE)

## Arguments

fun Function that returns a page argument. This function's argument list must include .... It should also include one or more named arguments that provide information for generating the new page: potential arguments include state, corresponding to the participant's state object, answer, which is the most recent participant response, and opt, which is the test's option list as created by test_options. The function should always return an object of class page. (Logical scalar) Whether to go to the next element in the timeline once this page is completed. This will typically be TRUE, except for special cases such as pages that load testing sessions from file (get_p_id).