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# Ceheiss's solution

## to Hello World in the Scheme Track

Published at Oct 30 2019 · 0 comments
Instructions
Test suite
Solution

#### Note:

This exercise has changed since this solution was written.

The classical introductory exercise. Just say "Hello, World!".

"Hello, World!" is the traditional first program for beginning programming in a new language or environment.

The objectives are simple:

• Write a function that returns the string "Hello, World!".
• Run the test suite and make sure that it succeeds.
• Submit your solution and check it at the website.

If everything goes well, you will be ready to fetch your first real exercise.

## Track Specific Notes

Your solution may be a procedure that returns the desired string or a variable whose value is that string.

## Running and testing your solutions

### From the command line

Simply type `make chez` if you're using ChezScheme or `make guile` if you're using GNU Guile. Sometimes the name for the scheme binary on your system will differ from the defaults. When this is the case, you'll need to tell make by running `make chez chez=your-chez-binary` or `make guile guile=your-guile-binary`.

### From a REPL

• Enter `(load "test.scm")` at the repl prompt.
• Develop your solution in `hello-world.scm` reloading as you go.
• Run `(test)` to check your solution.

## Source

This is an exercise to introduce users to using Exercism http://en.wikipedia.org/wiki/%22Hello,_world!%22_program

## Submitting Incomplete Solutions

It's possible to submit an incomplete solution so you can see how others have completed the exercise.

### test.scm

``````(import (rnrs))

(define test-fields '(input output who))

(define (test-run-solution solution input)
(if (procedure? solution) (apply solution input) solution))

(define (test-success description success-predicate
procedure input output)
(call/cc
(lambda (k)
(with-exception-handler
(lambda (e)
(k `(fail
(description . ,description)
(input . ,input)
(output . ,output)
(who . ,procedure))))
(lambda ()
(let ([result (test-run-solution procedure input)])
(unless (success-predicate result output)
(error 'exercism-test
"test fails"
description
input
result
output)))
`(pass . ,description))))))

(define (test-error description procedure input)
(call/cc
(lambda (k)
(with-exception-handler
(lambda (e) (k `(pass . ,description)))
(lambda ()
(test-run-solution procedure input)
`(fail
(description . ,description)
(input . ,input)
(output . error)
(who . ,procedure)))))))

(define (run-test-suite tests . query)
(for-each
(lambda (field)
(unless (and (symbol? field) (memq field test-fields))
(error 'run-test-suite
(format #t "~a not in ~a" field test-fields))))
query)
(let-values ([(passes failures)
(partition
(lambda (result) (eq? 'pass (car result)))
(map (lambda (test) (test)) tests))])
(cond
[(null? failures) (format #t "~%Well done!~%~%")]
[else
(format
#t
"~%Passed ~a/~a tests.~%~%The following test cases failed:~%~%"
(length passes)
(length tests))
(for-each
(lambda (failure)
(format
#t
"* ~a~%"
(cond
[(assoc 'description (cdr failure)) => cdr]
[else (cdr failure)]))
(for-each
(lambda (field)
(let ([info (assoc field (cdr failure))])
(format #t "  - ~a: ~a~%" (car info) (cdr info))))
query))
failures)
(error 'test "incorrect solution")])))

(define hello-world)

(define (test . query)
(apply
run-test-suite
(list
(lambda ()
(test-success "Say Hi!" equal? hello-world '()
"Hello, World!")))
query))

(let ([args (command-line)])
(if (null? (cdr args))
(load "hello-world.scm")
(load (cadr args)))
(test 'input 'output))``````
``````(import (rnrs))

(define (hello-world) "Hello, World!")``````

## Community comments

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### What can you learn from this solution?

A huge amount can be learned from reading other peopleâ€™s code. This is why we wanted to give exercism users the option of making their solutions public.

Here are some questions to help you reflect on this solution and learn the most from it.

• What compromises have been made?
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