Consider this snippet:
#lang racket
(define (f i)
(if (> i 5)
0
(+ 1 (f (+ 1 i)))))
Here, the call to f is not in tail position, and when I debug, I see a growing stack of the form
(+ ...)
(f ...)
(f ...)
(f ...)
(f ...)
This is expected. However, when I hover over the beginning of the last line, a light purple arrow appears and points to the beginning of the function definition. If I understand the documentation correctly, it indicates tail position. What am I missing?
The form which is the last line is in tail position with respect to f. The recursive call to f, however, isn't: if you hover over the f you'll get a pale blue arrow which tells you that it's the same f the function is binding. Here's a screenshot showing both things:
All of the (if ...) form and both of its consequents are in tail position. The f is the same f defined by the function, but is not in tail position.
When you move to B and you see A ➯ B. It means you can find B's define in A.
When you move to A and you see A ➯ B. You can see variable bound occurrence.
