Positional factory function for class mx.interware.caudal.core.immutant_state.caudal-store-immutant.
(swap-in-evt! cache key f & args)
Atomically swaps the value associated to the key in the cache with the result of applying f, passing the current value as the first param along with any args, returning the new cached value. Function f should have no side effects, as it may be called multiple times. If the key is missing, the result of applying f to nil will be inserted atomically.