do

Use a do syntax with steps

Given a file named “main.scm” with:

(import (scheme base))

(define xs '(1 2 3 4 5 6 7 8 9 10 11))

(do ((xs xs (cdr xs))
     (y 0 (+ y (car xs))))
  ((null? xs)
    (write-u8 y)))

When I successfully run scheme main.scm

Then the stdout should contain exactly “B”.

Use a do syntax without a step

Given a file named “main.scm” with:

(import (scheme base))

(define y 0)

(do ((xs #(1 2 3 4 5 6 7 8 9 10 11))
     (i 0 (+ i 1)))
  ((= i (vector-length xs))
    (write-u8 y))
  (set! y (+ y (vector-ref xs i))))

When I successfully run scheme main.scm

Then the stdout should contain exactly “B”.