if

Use if expressions

Given a file named “main.scm” with:

(import (scheme base))

(write-u8 (if <value> 65 66))

When I successfully run stak main.scm

Then the stdout should contain exactly “<output>”.

Examples

value	output
#f	B
#t	A

Use nested if expressions

Given a file named “main.scm” with:

(import (scheme base))

(write-u8 <expression>)

When I successfully run stak main.scm

Then the stdout should contain exactly “<output>”.

Examples

expression	output
(if #t (if #t 65 67) 67)	A
(if #f 67 (if #f 67 66))	B

Use deeply nested if expressions

Given a file named “main.scm” with:

(import (scheme base))

(write-u8 <expression>)

When I successfully run stak main.scm

Then the stdout should contain exactly “<output>”.

Examples

expression	output
(if #t (if #t (if #t 65 67) 67) 67)	A
(if #f 67 (if #f 67 (if #f 67 66)))	B

Use a one-sided if expression

Given a file named “main.scm” with:

(import (scheme base))

(if <value> (write-u8 65))

When I successfully run stak main.scm

Then the stdout should contain exactly “<output>”.

Examples

value	output
#f
#t	A

Use sequenced if expressions

Given a file named “main.scm” with:

(import (scheme base))

(if <value1>
  (write-u8 65)
  (write-u8 66))
(if <value2>
  (write-u8 65)
  (write-u8 66))
(if <value3>
  (write-u8 65)
  (write-u8 66))

When I successfully run stak main.scm

Then the stdout should contain exactly “<output>”.

Examples

value1	value2	value3	output
#t	#t	#t	AAA
#t	#t	#f	AAB
#t	#f	#t	ABA
#t	#f	#f	ABB
#f	#t	#t	BAA
#f	#t	#f	BAB
#f	#f	#t	BBA
#f	#f	#f	BBB

Use deeply nested if expressions

Given a file named “main.scm” with:

(import (scheme base))

(if <value1>
  (begin
    (write-u8 65)
      (if <value2>
        (begin
          (write-u8 65)
          (if <value3>
            (write-u8 65)
            (write-u8 66)))
        (begin
          (write-u8 66)
          (if <value3>
            (write-u8 65)
            (write-u8 66)))))
  (begin
    (write-u8 66)
      (if <value2>
        (begin
          (write-u8 65)
          (if <value3>
            (write-u8 65)
            (write-u8 66)))
        (begin
          (write-u8 66)
          (if <value3>
            (write-u8 65)
            (write-u8 66))))))

When I successfully run stak main.scm

Then the stdout should contain exactly “<output>”.

Examples

value1	value2	value3	output
#t	#t	#t	AAA
#t	#t	#f	AAB
#t	#f	#t	ABA
#t	#f	#f	ABB
#f	#t	#t	BAA
#f	#t	#f	BAB
#f	#f	#t	BBA
#f	#f	#f	BBB

Use sequenced if expressions in a nested if expression

Given a file named “main.scm” with:

(import (scheme base))

(if <value1>
  (begin
    (write-u8 65)
    (if <value2>
      (write-u8 65)
      (write-u8 66))
    (if <value3>
      (write-u8 65)
      (write-u8 66)))
  (begin
    (write-u8 66)
    (if <value2>
      (write-u8 65)
      (write-u8 66))
    (if <value3>
      (write-u8 65)
      (write-u8 66))))

When I successfully run stak main.scm

Then the stdout should contain exactly “<output>”.

Examples

value1	value2	value3	output
#t	#t	#t	AAA
#t	#t	#f	AAB
#t	#f	#t	ABA
#t	#f	#f	ABB
#f	#t	#t	BAA
#f	#t	#f	BAB
#f	#f	#t	BBA
#f	#f	#f	BBB