Chapter 10: Add the brief introduction of loop macro with examples

Just loop valid commands with the result assigned. In the next section
I'll add the life simulation to the repository.

land-of-lisp/cap10-loop.lisp

@@ -1,2 +1,93 @@
 ;; Common Lisp Script
-;; Manoel Vilela
+;; Manoel Vilela
+
+;; the loop macro
+
+(loop for i
+      below 5
+      sum i)
+;; => 10
+
+
+;; counting from a starting point to an ending point
+
+(loop for i
+      from 5
+      to 10
+      sum i)
+;; => 45
+
+;; iterating through values in a list
+
+(loop for i
+      in '(100 20 3)
+      sum i)
+;; => 123
+
+
+;; doing stuff in a loop
+
+(loop for i
+        below 5
+      do (print i))
+;; => nil
+;; print 0..5 on stdout
+
+;; doing stuff under certain conditions
+
+(loop for i
+        below 10
+      when (oddp i)
+        sum i)
+;; => 25
+
+;; breaking out of a loop early
+
+(loop for i
+      from 0
+      do (print i)
+      when (= i 5)
+        return 'falafel)
+;; => 'FALAFEL
+;; printing 0 to 5 on stdout
+
+;; collecting a list of values
+(loop for i
+      in '(2 3 4 5 6)
+      collect (* i i))
+;; => (4 9 16 25 36)
+
+
+;; using multiple for clauses
+
+(loop for x below 10
+      for y below 10
+      collect (+ x y))
+;; => (0 2 4 6 8 10 12 14 16 18)
+
+;; nested loop
+(loop for x below 10
+      collect (loop for y below 10
+                    collect (+ x y)))
+
+;; => ((0 1 2 3 4 5 6 7 8 9) (1 2 3 4 5 6 7 8 9 10)
+;;     (2 3 4 5 6 7 8 9 10 11) (3 4 5 6 7 8 9 10 11 12)
+;;     (4 5 6 7 8 9 10 11 12 13) (5 6 7 8 9 10 11 12 13 14)
+;;     (6 7 8 9 10 11 12 13 14 15) (7 8 9 10 11 12 13 14 15 16)
+;;     (8 9 10 11 12 13 14 15 16 17) (9 10 11 12 13 14 15 16 17 18))
+
+(loop for i
+      from 0
+      for day
+        in '(monday tuesday wednesday thursday friday saturday sunday)
+      collect (cons i day))
+
+;; => ((0 . MONDAY) (1 . TUESDAY) (2 . WEDNESDAY)
+;;     (3 . THURSDAY) (4 . FRIDAY) (5 . SATURDAY) (6 . SUNDAY))
+
+
+;; Well, this is just the brief introduction to loop macro on Land of Lisp.
+;; The book covers this chapter with this, a periodic table-like for loop
+;; with a lot of examples and on the final a life simulation. I'll cover
+;; that on the next file. See you in soon.
+;; EOF