There are two ways a for loop like that implemented: The first way, which I prefer, is to make the binding of i to its value inside the loop body, this way you

There are two ways a for loop like that implemented: The first way, which I prefer, is to make the binding of i to its value inside the loop body, this way you get a nice fresh binding on each loop iteration, so if you iterate the loop 5 time you get 5 bindings. The other way, which I loathe but is still an arguably "correct" way to do it, is to make one binding of i outside of the loop and then modify it on each loop iteration, so no matter how many iterations of the loop you have, there's only one binding. As far as I'm concerned, the first implementation is obviously the better one because the instances where this benefits you come often while the instances where the second implementation benefits you is very rare and unidiomatic. I think the second implementation is used for better performance but that's a mistake. I had this problem of perceptions when I switched from Common Lisp's Loop to Iterate. Loop, for all its many big shortcomings, had the decency of making a fresh binding on each new iteration, though IIRC the standard specifies that bindings can be established outside or inside the loop context. When I want to make a closure based on the value of an iterated variable with Iterate I have to do an explicit binding...