parse.scm

(import (chicken string))
(import (chicken condition))

(define (check-is-approved number approved-numbers)
    (cond ((equal? (length approved-numbers) 0)
           #f)
          ((equal? (car approved-numbers) number)
           #t)
          (else (check-is-approved number (cdr approved-numbers)))))

(define (convert-to-approved-numbers string-list approved-numbers)
    (let convert-to-approved-loop ((number-list (list))
                                   (string-list string-list)
                                   (approved-numbers approved-numbers))
        (if (equal? (length string-list) 0)
            number-list
            (let ((number (string->number (car string-list))))
                (if (check-is-approved number approved-numbers)
                    (convert-to-approved-loop (append number-list (list number)) (cdr string-list) approved-numbers)
                    (abort "must use integers 1:10 inclusive"))))))

(define (parse-small-arg arg)
    (define approved-small-numbers (list 1 2 3 4 5 6 7 8 9 10))
    (convert-to-approved-numbers (string-split arg ",") approved-small-numbers))

(define (parse-large-arg arg)
    (define approved-large-numbers (list 25 50 75 100))
    (convert-to-approved-numbers (string-split arg ",") approved-large-numbers))

(define (parse-numeric-arg arg)
    (string->number arg))

(define (parse-target-arg arg)
    (define min 100) 
    (define max 999) 
    (define target (parse-numeric-arg arg))
    (if (or (< target min) (> target max))
        (abort "Target is out of approved range")
        target))

(define (expr->string expression)
    (let to-string-loop ((str "")
                         (expression expression))
        (define to-add "")
        (if (null? expression)
            str
            (let ((symbol (car expression)))
                 (cond ((equal? symbol +)
                        (set! to-add "+"))
                       ((equal? symbol -)
                        (set! to-add "-"))
                       ((equal? symbol *)
                        (set! to-add "*"))
                       ((equal? symbol /)
                        (set! to-add "/"))
                       (else (set! to-add (number->string symbol))))
                 (to-string-loop (conc (conc str to-add) " ") (cdr expression))))))