Reactive programs don't have to be declarative. You can express a reactive program imperatively.
The defining feature of a reactive program is that relationships between inputs and outputs are automatically tracked, and changing an input will automatically update the dependent outputs.
Facebook had a whole experimental language (now abandoned) for writing reactive programs with imperative code: http://skiplang.com/
The portion of comment I was replying to was "no start or end" . This is reactive programming.
Having said that, other than Excel and some cute UI things, I've not seen much utility in reactive paradigms. Hence I am bearish on reactive programming. Someone please correct me.
