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:
If everything goes well, you will be ready to fetch your first real exercise.
Your solution may be a procedure that returns the desired string or a variable whose value is that string.
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.
(load "test.scm")at the repl prompt.
hello-world.scmreloading as you go.
(test)to check your solution.
This is an exercise to introduce users to using Exercism http://en.wikipedia.org/wiki/%22Hello,_world!%22_program
It's possible to submit an incomplete solution so you can see how others have completed the exercise.
(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) 'implement-me!) (define hello-world (display "Hello, World!"))
A huge amount can be learned from reading other people’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.