Parameter

Make a parameter

Given a file named “main.scm” with:

(import (scheme base))

(write-u8 ((make-parameter 65)))

When I successfully run scheme main.scm

Then the stdout should contain exactly “A”.

Parameterize a procedure

Given a file named “main.scm” with:

(import (scheme base))

(define x (make-parameter 65))

(write-u8 (x))
(write-u8 (parameterize ((x 66)) (x)))
(write-u8 (x))

When I successfully run scheme main.scm

Then the stdout should contain exactly “ABA”.

Parameterize nested procedures

Given a file named “main.scm” with:

(import (scheme base))

(define x (make-parameter 65))

(write-u8 (x))
(parameterize ((x 66))
  (write-u8 (x))
  (parameterize ((x 67))
    (write-u8 (x)))
  (write-u8 (x)))
(write-u8 (x))

When I successfully run scheme main.scm

Then the stdout should contain exactly “ABCBA”.

Use multiple parameters

Given a file named “main.scm” with:

(import (scheme base))

(define x (make-parameter 65))
(define y (make-parameter 66))

(write-u8 (x))
(write-u8 (y))
(parameterize ((x 67) (y 68))
  (write-u8 (x))
  (write-u8 (y)))
(write-u8 (x))
(write-u8 (y))

When I successfully run scheme main.scm

Then the stdout should contain exactly “ABCDAB”.