How would you design a program that will take in a string of lower case letters and produce the string upside down?
so if I type in home
i get ǝɯoɥ upside down.
I've tried looking for in the book to get started, but nothing.
Try this, a bit of a brute-force approach but works quite well for uppercase, lowercase and number characters - all other characters are presented just as they come:
(define upside-map '#hash(
(#\a . #\ɐ) (#\b . #\q) (#\c . #\ɔ) (#\d . #\p) (#\e . #\ǝ) (#\f . #\ɟ)
(#\g . #\ƃ) (#\h . #\ɥ) (#\i . #\ı) (#\j . #\ɾ) (#\k . #\ʞ) (#\l . #\ן)
(#\m . #\ɯ) (#\n . #\u) (#\o . #\o) (#\p . #\d) (#\q . #\b) (#\r . #\ɹ)
(#\s . #\s) (#\t . #\ʇ) (#\u . #\n) (#\v . #\ʌ) (#\w . #\ʍ) (#\x . #\x)
(#\y . #\ʎ) (#\z . #\z) (#\A . #\∀) (#\B . #\𐐒) (#\C . #\Ɔ) (#\D . #\◖)
(#\E . #\Ǝ) (#\F . #\Ⅎ) (#\G . #\⅁) (#\H . #\H) (#\I . #\I) (#\J . #\s)
(#\K . #\⋊) (#\L . #\˥) (#\M . #\W) (#\N . #\N) (#\O . #\O) (#\P . #\Ԁ)
(#\Q . #\Ό) (#\R . #\ᴚ) (#\S . #\S) (#\T . #\⊥) (#\U . #\∩) (#\V . #\Λ)
(#\W . #\M) (#\X . #\X) (#\Y . #\⅄) (#\Z . #\Z) (#\0 . #\0) (#\1 . #\Ɩ)
(#\2 . #\ᄅ) (#\3 . #\Ɛ) (#\4 . #\ㄣ) (#\5 . #\ϛ) (#\6 . #\9) (#\7 . #\ㄥ)
(#\8 . #\8) (#\9 . #\6)))
(define (flip-string str)
(list->string
(map (lambda (c)
(hash-ref upside-map c (const c)))
(reverse (string->list str)))))
For example:
(flip-string "Hello World")
=> "pןɹoM oןןǝH"
For reference, I used this conversion table taken from Wikipedia.