I came away with a different interpretation of Rich Hickey’s talk. I think he was advocating against using slots, where a slot would be a struct field. A slot h

I came away with a different interpretation of Rich Hickey’s talk. I think he was advocating against using slots, where a slot would be a struct field. A slot has to have a value and if a value is not available then null is put there and now null must be dealt with. Instead I think he was advocating for using dictionaries. You either have a key or you don’t, but you never use null. However it seems that now you would have a bunch of “key in dict” checks which are less efficient than “value is null” checks. Plus confusion about what exactly has been supplied in a dictionary. Although there may be cases where code can just sequence through what exists without worrying about what doesn’t exist.