球拍-大写

Question

; defining the procedure char_toupper to convert a lower case character to upper case
(define char_toupper (lambda (myChar)
                       ; defining x as the ASCII value of myChar
                       (define x (char->integer myChar))
                       ; defining y as x-32
                       (define y (- x 32))
                       ; if statement for while x is less than 91 (already uppercase)
                       (if (< x 91)
                            ; if it is already uppercase, just display it
                            (display myChar)
                            ; otherwise, if x is greater than 96 (lowercase)
                            (if (> x 96)
                                ; then display the character equivalent to the ASCII value given by y
                                (display (integer->char y))))))

(define string_toupper (lambda (myString newString i)       
                         (if (< i (string-length myString))
                             (string_toupper myString (string-append newString (char_toupper (string-ref myString i))) (+ 1 i)))

                         (display newString)))
(string_toupper (read) "" 0)

这会将每个字符转换为大写，并显示它。但我不断收到错误，我可以找到它。任何帮助。谢谢

Answer 1

在 Racket 中，你必须写 when 而不是在单臂情况下的 if。

即把下面表达式中的if改为when。

(if (> x 96)
    ; then display the character equivalent to the ASCII value given by y
    (display (integer->char y)))

还要注意string-upcase 是内置的。