Continuation

Call a continuation

Given a file named “main.scm” with:

(import (scheme base))

(write-u8 (call/cc (lambda (k) (k 65))))

When I successfully run scheme main.scm

Then the stdout should contain exactly “A”.

Call a continuation with a global variable

Given a file named “main.scm” with:

(import (scheme base))

(define x 5)

(write-u8 (+ 60 (call/cc (lambda (k) (k x)))))

When I successfully run scheme main.scm

Then the stdout should contain exactly “A”.

Call a continuation with a local variable

Given a file named “main.scm” with:

(import (scheme base))

(define (f x) (call/cc (lambda (k) (k x))))

(write-u8 (+ 60 (f 5)))

When I successfully run scheme main.scm

Then the stdout should contain exactly “A”.

Return a value from a receiver

Given a file named “main.scm” with:

(import (scheme base))

(write-u8 (call/cc (lambda (k) 65)))

When I successfully run scheme main.scm

Then the stdout should contain exactly “A”.

Modify environment

Given a file named “main.scm” with:

(import (scheme base))

(define backtrack #f)

(let ((i 65))
  (call/cc
    (lambda (target)
      (set! backtrack target)
      #f))
  (write-u8 i)
  (set! i (+ i 1))
  (if (< i 91)
    (backtrack #f)
    #f))

When I successfully run scheme main.scm

Then the stdout should contain exactly:

ABCDEFGHIJKLMNOPQRSTUVWXYZ