I've read a lot of good things about Land of Lisp so I thought that I might go through it to see what there was to see.
(defun tweak-text (lst caps lit)
(when lst
(let ((item (car lst))
(rest (cdr lst)))
(cond
; If item = space, then call recursively starting with ret
; Then, prepend the space on to the result.
((eq item #\space) (cons item (tweak-text rest caps lit)))
; if the item is an exclamation point. Make sure that the
; next non-space is capitalized.
((member item '(#\! #\? #\.)) (cons item (tweak-text rest t lit)))
; if item = " then toggle whether we are in literal mode
((eq item #\") (tweak-text rest caps (not lit)))
; if literal mode, just add the item as is and continue
(lit (cons item (tweak-text rest nil lit)))
; if either caps or literal mode = true capitalize it?
((or caps lit) (cons (char-upcase item) (tweak-text rest nil lit)))
; otherwise lower-case it.
(t (cons (char-downcase item) (tweak-text rest nil nil)))))))
(the comments are mine)
(FYI -- the method signature is (list-of-symbols bool-whether-to-caps bool-whether-to-treat-literally) but the author shortened these to (lst caps lit).)
But anyway, here's the question:
This has (cond... (lit ...) ((or caps lit) ...)) in it. My understanding is that this would translate to if(lit){ ... } else if(caps || lit){...} in a C style syntax. Isn't the or statement redundant then? Is there ever a condition where the (or caps lit) condition will be called if caps is nil?
Indeed, you are correct. See the errata for the book.
Page 97: The function tweak-text has two glitches in it, though it will run OK on most Lisp implementations. First of all, it uses the eq function to compare characters- Characters should always be checked with other functions such as eql or char-equal as per the ANSI spec. Also, there's an unnecessary check of (or caps lit) that can be simplified to caps.