tasks a-s

Task/S-Expressions/Common-Lisp/s-expressions-1.lisp

@@ -0,0 +1,5 @@
+(defun lsquare-reader (stream char)
+  (declare (ignore char))
+  (read-delimited-list #\] stream t))
+(set-macro-character #\[ #'lsquare-reader)               ;;Call the lsquare-reader function when a '[' token is parsed
+(set-macro-character #\] (get-macro-character #\) nil))  ;;Do the same thing as ')' when a ']' token is parsed

Task/S-Expressions/Common-Lisp/s-expressions-2.lisp

@@ -0,0 +1,16 @@
+;;A list of unit tests.  Each test is a cons in which the car (left side) contains the
+;;test string and the cdr (right side) the expected result of reading the S-Exp.
+(setf unit-tests
+      (list
+       (cons "[]" NIL)
+       (cons "[a b c]" '(a b c))
+       (cons "[\"abc\" \"def\"]" '("abc" "def"))
+       (cons "[1 2 [3 4 [5]]]" '(1 2 (3 4 (5))))
+       (cons "[\"(\" 1 2 \")\"]" '("(" 1 2 ")"))
+       (cons "[4/8 3/6 2/4]" '(1/2 1/2 1/2))
+       (cons "[reduce #'+ '[1 2 3]]" '(reduce #'+ '(1 2 3)))))
+
+(defun run-tests ()
+  (dolist (test unit-tests)
+    (format t "String: ~23s  Expected: ~23s  Actual: ~s~%"
+	    (car test) (cdr test) (read-from-string (car test)))))

Task/S-Expressions/Common-Lisp/s-expressions-3.lisp

@@ -0,0 +1,24 @@
+(defun write-sexp (sexp)
+  "Writes a Lisp s-expression in square bracket notation."
+  (labels ((parse (sexp)
+	     (cond ((null sexp) "")
+		   ((atom sexp) (format nil "~s " sexp))
+		   ((listp sexp)
+		    (concatenate
+		     'string
+		     (if (listp (car sexp))
+			 (concatenate 'string "["
+				      (fix-spacing (parse (car sexp)))
+				      "] ")
+			 (parse (car sexp)))
+		     (parse (cdr sexp))))))
+	   (fix-spacing (str)
+	     (let ((empty-string ""))
+	       (unless (null str)
+		 (if (equal str empty-string)
+		     empty-string
+		     (let ((last-char (1- (length str))))
+		       (if (eq #\Space (char str last-char))
+			   (subseq str 0 last-char)
+			   str)))))))
+    (concatenate 'string "[" (fix-spacing (parse sexp)) "]")))

Task/S-Expressions/Common-Lisp/s-expressions-4.lisp

@@ -0,0 +1,7 @@
+(setf unit-tests '(((1 2) (3 4)) (1 2 3 4) ("ab(cd" "mn)op")
+		   (1 (2 (3 (4)))) ((1) (2) (3)) ()))
+
+(defun run-tests ()
+  (dolist (test unit-tests)
+    (format t "Before: ~18s  After: ~s~%"
+	    test (write-sexp test))))