Added lisp along with some study work

lisp/ansi_lisp/ch3/notes.txt

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+(eql x y) -- Tests of it's the same object
+
+(setf x '(a b c))
+(setf y x) -- This will copy the poiner, so any changes to either will affect the other.
+
+(setf x '(a b c)
+			y (copy-list x)) -- This will actually create a new list (eql x y) will return nil
+
+(append '(a b) '(c d) '(e)) -- append lists together. Will result in a single combined list.
+
+(nth 0 '(a b c)) -- Find the nth element. In this cas 'A'
+(nthcdr 1 '(a b c)) -- Find the nth cdr. In this case (B C)
+
+(zerop n) -- Checks if value is 0
+(last '(a b c)) -- Returns last cons in a list. So it'll return "(C) here
+(car(last '(a b c))) -- Returns last element of a list. In this case "C"
+
+--first - tenth are defined as functions that are not zero indexed so for example:
+(fifth '(a b c d e f g h i)) -- Will return "E" (the element, not the cons)
+
+(mapcar #'(lambda (x) (+ x 10))
+				'(1 2 3)) -- Takes a function and applies everything in the list to it. In this case it will return (11 12 13)
+
+(mapcar #'list
+				'(a b c)
+				'(1 2 3 4)) -- Would return:
+				((A1) (B2) (C 3)) 
+
+(member 'b '(a b c d e)) -- (member) finds what it's looking for, and returns it as well as the cdr from that point. So here we would see "b" - "e"
+
+-- Keywords are a symbol preceded by a colon... so ":test" for example
+-- Member defaults to testing with eql, perhaps we want equal instead:
+-- NOTE: Equal is less strict than eql. Equal returns true if it's arguemnts print the same.
+-- EQL only if they are the same object
+(member '(a) '((a) (z)) :test #'equal) -- Will result in ((A) (Z))
+
+--There is also :key
+(member 'a '((a b) (c d)) :key #'car) -- will return ((A B) (C D)) -- We asked if there was an element whose car was a
+-- keywords are always at the end, and multiple are acceptable.
+
+If we want to find an element satisfying an arbitrary predicate, like oddp, which returns true for odd ints, we can use member-if
+
+(member-if #'oddp '(2 3 4)) -- This will find the first odd number, 3 in this case, and return it along with the rest of the list
+
+(adjoin) -- conses an object into a list if it's not already a member
+(adjoin 'b '(a b c)) -- (A B C)
+(adjoin 'z '(a b c)) -- (Z A B C)
+
+(union '(a b c) '(c b s)) -- (A C B S)
+(intersection '(a b c) '(b b c)) -- (B C)
+(set-difference '(a b c d e) '(b e)) -- (A C D) -- So, expected stuff
+-- The above creates sets, and as we know, sets have no specific order
+
+(length ' (a b c)) -- 3
+
+-- Grab a part of a list
+-- Think python slices, third  argument (second number) is optional.
+(subseq '(a b c d) 1 2) -- (B)
+(subseq '(a b c d) 1) -- (B C D) 
+
+(reverse '(a b c)) -- Obvious, returns (A B C)
+
+(subseq(reverse '(a b c)) 0 2) -- (C B) -- A way to grab the last two
+(subseq(reverse '(a b c)) 1) -- (B A) -- Start with second to last and go backwards. Basically cut off the last (or however many ) element 
+
+(sort '(0 2 1 3 8) #'>) -- (8 3 2 1 0) -- Is destructive to the origional list. Of course, < would sort in order
+
+(every #'oddp '(1 3 5)) -- Are they all odd? -- True
+(some #'evenp '(1 2 3)) -- Are some of the even? -- True
+
+(every #'> '(1 3 5) '(0 2 4)) -- Think math, is every element greater than it's corresponding element so...
+-- is 1 > 0? AND is 3 >2 AND is 5>4? True
+If sequences are different lengths, the shortests determines how many tests are performed.
+
+(push x y) push object x onto the front of list y
+(pop x) -- remove and return the first element of list x
+
+(let ((x '(a b)))
+	(pushnew 'c x)
+	(pushnew 'a x)
+	x) -- This will only push to "x" if the object doesn't already exist.
+
+-- Conses are not just for building lists, an improper list, or dotted list, can be used make a structure with two fields
+(setf pair (cons 'a 'b)) -- (A . B)
+-- car will return A, while cdr will return B