Adding time with mutable local variables is along the same axis as having mutable state in objects, only more fine-grained in the call stack. Yes you can write algorithms like this, if you like playing the computer ticker tape game.

These modern languages with lambdas are what enable writing in a functional style. One can choose to use single-assignment 'var's and map/filter etc, at that point you're not using the procedural aspect of the language which is great, but why not start with a language that more than allows it.