In the author's mind, it's unexpected/amazing that 'for' can iterate over many types. But it's NOT unexpected/amazing that 'iter' can iterate over many types. I have no idea why.

It's not like 'for' is limited to counting in other languages. The grand-daddy in c does something until some condition is false, and that thing can equally be incrementing/decrementing a number or invoking some function. That's what a loop does in any case, it compiles down to a conditional jump (JNE/JE..)

Maybe his reason for astonishment is obscured by over-use of an LLM to 'enhance' the text.

Why would it ever be surprising that I can y= [x,x,y,y] for x in y; x=y; return y;

and get [y,y,y,y]?

> It's not like 'for' is limited to counting in other languages. The grand-daddy in c does something until some condition is false

C 'for' is a while loop. It's strictly syntactic sugar for an already existing feature. And it's really, really transparent. `for(A; B; C) { do_stuff(); }` isn't just a while loop, it's this while loop:

    A;
    while(B) {
      do_stuff();
      C;
    }