ignoring nested music thing

dice - more practice with signal and clog
backquote - first practice with @,a splicing
macros - some news of common errors:
- capturing outer symbols, so caller expects them to be used, but
invisible internal values take their place
- evaluating "pass by name" forms too many times
- evaluating them in surprising order

.gitignore

@@ -1 +1,2 @@
 /.direnv/
+/music/

lisp-koans/koans/backquote.lisp

@@ -19,23 +19,26 @@
   (let ((x '(123))
         (z '(7 8 9)))
     ;; ' quotes an expression normally.
-    (assert-equal ____ '(x 45 6 z))
+    (assert-equal (list 'x 45 6 'z) '(x 45 6 z))
     ;; ` backquotes an expression; without any unquotes, it is equivalent to
     ;; using the normal quote.
-    (assert-equal ____ `(x 45 6 z))
+    (assert-equal '(x 45 6 z) `(x 45 6 z))
     ;; , unquotes a part of the expression.
-    (assert-equal ____ `(,x 45 6 z))
+    (assert-equal '((123) 45 6 z) `(,x 45 6 z))
-    (assert-equal ____ `(,x 45 6 ,z))
+    (assert-equal '((123) 45 6 (7 8 9)) `(,x 45 6 ,z))
     ;; ,@ splices an expression into the into the list surrounding it.
-    (assert-equal ____ `(,x 45 6 ,@z))
+    (assert-equal '((123) 45 6 7 8 9) `(,x 45 6 ,@z))
-    (assert-equal ____ `(,@x 45 6 ,@z))))
+    (assert-equal '(123 45 6 7 8 9) `(,@x 45 6 ,@z))))
 
 (define-test backquote-forms
   ;; Because of its properties, backquote is useful for constructing Lisp forms
   ;; that are macroexpansions or parts of macroexpansions.
   (let ((variable 'x))
     ;; Fill in the blank without without using backquote/unquote notation.
-    (assert-equal ____
+    (assert-equal '(if (typep x 'string)
+                    (format nil "The value of ~A is ~A" 'x x)
+                    (error 'type-error :datum x
+                     :expected-type 'string))
                   `(if (typep ,variable 'string)
                        (format nil "The value of ~A is ~A" ',variable ,variable)
                        (error 'type-error :datum ,variable
@@ -43,7 +46,9 @@
   (let ((error-type 'type-error)
         (error-arguments '(:datum x :expected-type 'string)))
     ;; Fill in the blank without without using backquote/unquote notation.
-    (assert-equal ____
+    (assert-equal '(if (typep x 'string)
+                    (format nil "The value of ~A is ~A" 'x x)
+                    (error 'type-error :datum x :expected-type 'string))
                   `(if (typep x 'string)
                        (format nil "The value of ~A is ~A" 'x x)
                        (error ',error-type ,@error-arguments)))))
@@ -51,15 +56,15 @@
 (define-test numbers-and-words
   (let ((number 5)
         (word 'dolphin))
-    (true-or-false? ____ (equal '(1 3 5) `(1 3 5)))
+    (true-or-false? t (equal '(1 3 5) `(1 3 5)))
-    (true-or-false? ____ (equal '(1 3 5) `(1 3 number)))
+    (true-or-false? nil (equal '(1 3 5) `(1 3 number)))
-    (assert-equal ____ `(1 3 ,number))
+    (assert-equal '(1 3 5) `(1 3 ,number))
-    (assert-equal _____ `(word ,word ,word word))))
+    (assert-equal '(word dolphin dolphin word) `(word ,word ,word word))))
 
 (define-test splicing
   (let ((axis '(x y z)))
-    (assert-equal '(the axis are ____) `(the axis are ,axis))
+    (assert-equal '(the axis are (x y z)) `(the axis are ,axis))
-    (assert-equal '(the axis are ____) `(the axis are ,@axis)))
+    (assert-equal '(the axis are x y z) `(the axis are ,@axis)))
   (let ((coordinates '((43.15 77.6) (42.36 71.06))))
-    (assert-equal ____ `(the coordinates are ,coordinates))
+    (assert-equal '(the coordinates are ((43.15 77.6) (42.36 71.06))) `(the coordinates are ,coordinates))
-    (assert-equal ____ `(the coordinates are ,@coordinates))))
+    (assert-equal '(the coordinates are (43.15 77.6) (42.36 71.06)) `(the coordinates are ,@coordinates))))

lisp-koans/koans/condition-handlers.lisp

@@ -101,7 +101,7 @@
                      (very-silly-condition #'handle-very-silly-condition)
                      (most-silly-condition #'handle-most-silly-condition))
         (signal (make-condition 'most-silly-condition)))
-      (assert-equal ____ *list*)))
+      (assert-equal '(:most-silly-condition :very-silly-condition :silly-condition) *list*)))
 
 (define-test multiple-handler-binds
   ;; It is possible to bind handlers in steps.
@@ -110,7 +110,7 @@
                    (most-silly-condition #'handle-most-silly-condition))
       (handler-bind ((very-silly-condition #'handle-very-silly-condition))
         (signal (make-condition 'most-silly-condition))))
-    (assert-equal ____ *list*)))
+    (assert-equal '(:most-silly-condition :silly-condition :very-silly-condition) *list*)))
 
 (define-test same-handler
   ;; The same handler may be bound multiple times.
@@ -121,7 +121,7 @@
                      (silly-condition #'handle-silly-condition)
                      (very-silly-condition #'handle-very-silly-condition))
         (signal (make-condition 'most-silly-condition))))
-    (assert-equal ____ *list*)))
+    (assert-equal '(:silly-condition :silly-condition :very-silly-condition :silly-condition :very-silly-condition ) *list*)))
 
 (define-test handler-types
   ;; A handler is not executed if it does not match the condition type.
@@ -130,7 +130,7 @@
                    (very-silly-condition #'handle-very-silly-condition)
                    (most-silly-condition #'handle-most-silly-condition))
       (signal (make-condition 'very-silly-condition)))
-    (assert-equal ____ *list*)))
+    (assert-equal '(:very-silly-condition :silly-condition) *list*)))
 
 (define-test handler-transfer-of-control
   ;; A handler may decline to handle the condition if it returns normally,
@@ -143,7 +143,7 @@
                                         (return-from my-block)))
                      (silly-condition #'handle-silly-condition))
         (signal (make-condition 'silly-condition))))
-    (assert-equal ____ *list*)))
+    (assert-equal '(:silly-condition) *list*)))
 
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 
@@ -163,7 +163,7 @@
     (handler-case (signal (make-condition 'my-error))
       (error (condition) (handle-error condition))
       (my-error (condition) (handle-my-error condition)))
-    (assert-equal ____ *list*)))
+    (assert-equal '(:error) *list*)))   ; well, I don't really understand that
 
 (define-test handler-case-order
   ;; The order of handler cases matters.
@@ -171,7 +171,7 @@
     (handler-case (signal (make-condition 'my-error))
       (my-error (condition) (handle-my-error condition))
       (error (condition) (handle-error condition)))
-    (assert-equal ____ *list*)))
+    (assert-equal '(:my-error) *list*)))
 
 (define-test handler-case-type
   ;; A handler cases is not executed if it does not match the condition type.
@@ -179,7 +179,16 @@
     (handler-case (signal (make-condition 'error))
       (my-error (condition) (handle-my-error condition))
       (error (condition) (handle-error condition)))
-    (assert-equal ____ *list*)))
+    (assert-equal '(:error) *list*)))
+
+;;; it seems that difference between #'handler-case and #'handler-bind
+;; is that first is like try-catch, where single, first condition for signal is executed
+;; (and expressions are not handlers, but things to evaluate)
+;; and handler-bind executes all handlers applicable?
+;; here handlers are functions
+;; http://www.lispworks.com/documentation/HyperSpec/Body/09_ada.htm
+;; here it seems that handler can either transfer control - by return-from of return
+;; and that "handles" the signal, or "decline" by returning, that that means that following handlers get called
 
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 
@@ -199,36 +208,37 @@
            (handler-case (divide numerator denominator)
              (division-by-zero () :division-by-zero)
              (type-error () :type-error))))
-    (assert-equal ____ (try-to-divide 6 2))
+    (assert-equal 3 (try-to-divide 6 2))
-    (assert-equal ____ (try-to-divide 6 0))
+    (assert-equal :division-by-zero (try-to-divide 6 0))
-    (assert-equal ____ (try-to-divide 6 :zero))))
+    (assert-equal :type-error (try-to-divide 6 :zero))))
 
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 
 ;;; Condition objects can contain metadata about the specific situation that
 ;;; occurred in the code.
-
 (define-test accessors-division-by-zero
-  (let ((condition (handler-case (divide 6 0) (division-by-zero (c) c))))
+    (setq my-cond (handler-case (divide 6 0) (division-by-zero (c) c)))
+  (let ((my-cond (handler-case (divide 6 0) (division-by-zero (c) c))))
     ;; Disabled on CLISP and ABCL due to conformance bugs.
     ;; See https://gitlab.com/gnu-clisp/clisp/-/issues/22
     ;; See https://github.com/armedbear/abcl/issues/177
     #-(or clisp abcl)
-    (assert-equal ____ (arithmetic-error-operands condition))
+    (assert-equal '(6 0) (arithmetic-error-operands my-cond)) ; returns '(6 0)
-    (let ((operation (arithmetic-error-operation condition)))
+    (let ((operation (arithmetic-error-operation my-cond))) ; returns #'/ holy cow
       ;; Disabled on ABCL due to a conformance bug.
       ;; See https://github.com/armedbear/abcl/issues/177
       #-abcl
-      (assert-equal ____ (funcall operation 12 4)))))
+      (assert-equal 3 (funcall operation 12 4)))))
 
+(setq my-condition (handler-case (divide 6 :zero) (type-error (c) c)))
 (define-test accessors-type-error
   (let ((condition (handler-case (divide 6 :zero) (type-error (c) c))))
-    (assert-equal ____ (type-error-datum condition))
+    (assert-equal :zero (type-error-datum my-condition))
-    (let ((expected-type (type-error-expected-type condition)))
+    (let ((expected-type (type-error-expected-type my-condition)))
-      (true-or-false? ____ (typep :zero expected-type))
+      (true-or-false? nil (typep :zero expected-type))
-      (true-or-false? ____ (typep 0 expected-type))
+      (true-or-false? t (typep 0 expected-type))
-      (true-or-false? ____ (typep "zero" expected-type))
+      (true-or-false? nil (typep "zero" expected-type))
-      (true-or-false? ____ (typep 0.0 expected-type)))))
+      (true-or-false? t (typep 0.0 expected-type)))))
 
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 
@@ -256,12 +266,12 @@
   (flet ((try-log-line-type (line)
            (handler-case (log-line-type line)
              (error (condition) condition))))
-    (assert-equal ____ (try-log-line-type "TIMESTAMP 2020-05-08 16:59:39"))
+    (assert-equal :timestamp (try-log-line-type "TIMESTAMP 2020-05-08 16:59:39"))
-    (assert-equal ____ (try-log-line-type "HTTP GET / from 127.0.0.1"))
+    (assert-equal :http (try-log-line-type "HTTP GET / from 127.0.0.1"))
-    (assert-equal ____ (try-log-line-type "LOGIN administrator:hunter2"))
+    (assert-equal :login (try-log-line-type "LOGIN administrator:hunter2"))
     (let ((condition (try-log-line-type "WARNING: 95% of disk space used")))
-      (assert-equal ____ (line condition))
+      (assert-equal  "WARNING: 95% of disk space used" (line condition))
-      (assert-equal ____ (reason condition)))
+      (assert-equal :unknown-log-line-type (reason condition)))
     (let ((condition (try-log-line-type 5555)))
-      (assert-equal 'string (____ condition))
+      (assert-equal 'string (type-error-expected-type condition))
-      (assert-equal 5555 (____ condition)))))
+      (assert-equal 5555 (type-error-datum condition)))))

lisp-koans/koans/dice-project.lisp

@@ -18,20 +18,29 @@
 
 (defclass dice-set ()
   ;; Fill in the blank with a proper slot definition.
-  (____))
+  ((dice-values :initarg :dice-values)))
+
+(setq *my-dice* (make-instance 'dice-set :dice-values '(1 2 3 5)))
+(slot-value *my-dice* 'dice-values)
 
 ;;; This method might be unnecessary, depending on how you define the slots of
 ;;; DICE-SET.
 
 (defmethod dice-values ((object dice-set))
-  ____)
+  (slot-value object 'dice-values))
 
 (defmethod roll (count (object dice-set))
-  ____)
+  (unless (and (integerp count) (< 0 count)) (signal (make-condition 'type-error
+                                                   :datum count
+                                                   :expected-type 'integer)))
+  (let ((rolls (mapcar (lambda (x) (declare (ignore  x)) (+ 1 (random 6))) (make-list count))))
+    (setf (slot-value object 'dice-values) rolls)))
+
+(roll 5 *my-dice*)
 
 (define-test make-dice-set
-  (let ((dice (make-instance 'dice-set)))
+    (let ((dice (make-instance 'dice-set)))
-    (assert-true (typep dice 'dice-set))))
+      (assert-true (typep dice 'dice-set))))
 
 (define-test dice-are-six-sided
   (let ((dice (make-instance 'dice-set)))
@@ -73,21 +82,34 @@
     (assert-equal 100 (length (roll 100 dice)))
     (assert-equal 1 (length (roll 1 dice)))))
 
+;; this is about signaling error, rhg
+;; but wtf about expected-type being subtype of '(integer 1 6) ???
+;; shouldn't it be any integer?
+
+
+
 (define-test junk-as-dice-count
-  (let ((dice (make-instance 'dice-set)))
+    (let ((dice (make-instance 'dice-set)))
-    (labels ((dice-failure (count)
+      (labels ((dice-failure (count)
-               (handler-case (progn (roll count dice)
+                 (handler-case (progn (roll count dice)
-                                    (error "Test failure"))
+                                      (error "Test failure"))
-                 (error (condition) condition)))
+                   (error (condition) condition)))
-             (test-dice-failure (value)
+               (test-dice-failure (value)
-               (let* ((condition (dice-failure value))
+                 (let* ((condition (dice-failure value))
-                      (expected-type (type-error-expected-type condition)))
+                        (expected-type (type-error-expected-type condition)))
-                 (assert-true (typep condition 'type-error))
+                   (assert-true (typep condition 'type-error))
-                 (assert-equal value (type-error-datum condition))
+                   (assert-equal value (type-error-datum condition))
-                 (assert-true (subtypep '(integer 1 6) expected-type)))))
+                   (assert-true (subtypep '(integer 1 6) expected-type)) ; wtf is this?
-      (test-dice-failure 0)
+                                        ; surely it's got to be just integer?
-      (test-dice-failure "0")
+                   )))
-      (test-dice-failure :zero)
+        (test-dice-failure 0)
-      (test-dice-failure 18.0)
+        (test-dice-failure "0")
-      (test-dice-failure -7)
+        (test-dice-failure :zero)
-      (test-dice-failure '(6 6 6)))))
+        (test-dice-failure 18.0)
+        (test-dice-failure -7)
+        (test-dice-failure '(6 6 6)))))
+
+;; (setq dice *my-dice*)
+;; (dice-failure "0")
+
+;;; welp. signaling errors is the most unfamiliar thing for me

lisp-koans/koans/extra-credit.lisp

@@ -23,4 +23,4 @@
 ;;; This is a free form assignment, so approach it however you desire.
 
 (define-test play-greed
-  (assert-true ____))
+  (assert-true t))

lisp-koans/koans/macros.lisp

@@ -23,19 +23,22 @@
              (cond ((null forms) 'nil)
                    ((null (rest forms)) (first forms))
                    (t `(when ,(first forms)
-                         ,(generate (rest forms)))))))
+                         ,(generate (rest forms))))))) ; wowy
     (generate forms)))
 
+(when (= 2 3) "hello")
+
 (define-test my-and
-  ;; ASSERT-EXPANDS macroexpands the first form once and checks if it is equal
+    ;; ASSERT-EXPANDS macroexpands the first form once and checks if it is equal
-  ;; to the second form.
+    ;; to the second form.
-  (assert-expands (my-and (= 0 (random 6)) (error "Bang!"))
+    (assert-expands (my-and (= 0 (random 6)) (error "Bang!"))
-                  '(when (= 0 (random 6)) (error "Bang!")))
+                    '(when (= 0 (random 6)) (error "Bang!")))
   (assert-expands (my-and (= 0 (random 6))
                           (= 0 (random 6))
                           (= 0 (random 6))
                           (error "Bang!"))
-                  ____))
+                 '(when (= 0 (random 6))
+                   (when (= 0 (random 6)) (when (= 0 (random 6)) (error "Bang!"))))))
 
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 
@@ -43,16 +46,19 @@
 
 (define-test variable-capture
   (macrolet ((for ((var start stop) &body body)
-               `(do ((,var ,start (1+ ,var))
+                  `(do ((,var ,start (1+ ,var))
-                     (limit ,stop))
+                        (limit ,stop))
-                    ((> ,var limit))
+                       ((> ,var limit))
-                  ,@body)))
+                     ,@body)))
     (let ((limit 10)
           (result '()))
       (for (i 0 3)
-           (push i result)
+        (push i result)
-           (assert-equal ____ limit))
+        (assert-equal 3 limit))
-      (assert-equal ____ (nreverse result)))))
+      (assert-equal '(0 1 2 3) (nreverse result))))) ; didn't get it on first tries, ugh
+;; oh, ok - then try to use names that wouldn't happen in outside condext
+;; so that explicitly defined things in outside context get overshadowed
+;; ok
 
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 
@@ -60,20 +66,23 @@
 ;;; meant to be evaluated once.
 
 (define-test multiple-evaluation
-  ;; We use MACROLET for defining a local macro.
+    ;; We use MACROLET for defining a local macro.
-  (macrolet ((for ((var start stop) &body body)
+    (macrolet ((for ((var start stop) &body body)
-               `(do ((,var ,start (1+ ,var)))
+                 `(do ((,var ,start (1+ ,var)))
-                    ((> ,var ,stop))
+                      ((> ,var ,stop))
-                  ,@body)))
+                    ,@body)))
-    (let ((side-effects '())
+      (let ((side-effects '())
-          (result '()))
+            (result '()))
-      ;; Our functions RETURN-0 and RETURN-3 have side effects.
+        ;; Our functions RETURN-0 and RETURN-3 have side effects.
-      (flet ((return-0 () (push 0 side-effects) 0)
+        (flet ((return-0 () (push 0 side-effects) 0)
-             (return-3 () (push 3 side-effects) 3))
+               (return-3 () (push 3 side-effects) 3))
-        (for (i (return-0) (return-3))
+          (for (i (return-0) (return-3))
-          (push i result)))
+            (push i result)))
-      (assert-equal ____ (nreverse result))
+        (assert-equal '(0 1 2 3) (nreverse result))
-      (assert-equal ____ (nreverse side-effects)))))
+        (assert-equal '(0 3 3 3 3 3) (nreverse side-effects)))))
+                                        ; omg, fuck this guessing
+                                        ; ok, the ,stop was evaluated on each iteraction
+                                        ; to check "whether to stop"
 
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 
@@ -81,36 +90,53 @@
 ;;; subforms.
 
 (define-test wrong-evaluation-order
-  (macrolet ((for ((var start stop) &body body)
+    (macrolet ((for ((var start stop) &body body)
-               ;; The function GENSYM creates GENerated SYMbols, guaranteed to
+                 ;; The function GENSYM creates GENerated SYMbols, guaranteed to
-               ;; be unique in the whole Lisp system. Because of that, they
+                 ;; be unique in the whole Lisp system. Because of that, they
-               ;; cannot capture other symbols, preventing variable capture.
+                 ;; cannot capture other symbols, preventing variable capture.
-               (let ((limit (gensym "LIMIT")))
+                 (let ((limit (gensym "LIMIT")))
-                 `(do ((,limit ,stop)
+                   `(do ((,limit ,stop)
-                       (,var ,start (1+ ,var)))
+                         (,var ,start (1+ ,var)))
-                      ((> ,var ,limit))
+                        ((> ,var ,limit))
-                    ,@body))))
+                      ,@body))))
-    (let ((side-effects '())
+      (let ((side-effects '())
-          (result '()))
+            (result '()))
-      (flet ((return-0 () (push 0 side-effects) 0)
+        (flet ((return-0 () (push 0 side-effects) 0)
-             (return-3 () (push 3 side-effects) 3))
+               (return-3 () (push 3 side-effects) 3))
-        (for (i (return-0) (return-3))
+          (for (i (return-0) (return-3))
-          (push i result)))
+            (push i result)))
-      (assert-equal ____ (nreverse result))
+        (assert-equal '(0 1 2 3) (nreverse result))
-      (assert-equal ____ (nreverse side-effects)))))
+        (assert-equal '(3 0) (nreverse side-effects)))))
+;; didn't got on first try,
+;; but yes, for gensym limit ,stop is evaluated first
 
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 
 (define-test for
-  (macrolet ((for ((var start stop) &body body)
+    (macrolet ((for ((var start stop) &body body)
-               ;; Fill in the blank with a correct FOR macroexpansion that is
+                 ;; Fill in the blank with a correct FOR macroexpansion that is
-               ;; not affected by the three macro pitfalls mentioned above.
+                 ;; not affected by the three macro pitfalls mentioned above.
-               ____))
+                 (let ((initial (gensym "INITIAL"))
-    (let ((side-effects '())
+                       (limit (gensym "LIMIT")))
-          (result '()))
+                   `(do* ((,initial ,start)
-      (flet ((return-0 () (push 0 side-effects) 0)
+                         (,limit ,stop)
-             (return-3 () (push 3 side-effects) 3))
+                         (,var ,initial (1+ ,var)))
-        (for (i (return-0) (return-3))
+                        ((> ,var ,limit))
-          (push i result)))
+                      ,@body))))
-      (assert-equal '(0 1 2 3) (nreverse result))
+      (let ((side-effects '())
-      (assert-equal '(0 3) (nreverse side-effects)))))
+            (result '()))
+        (flet ((return-0 () (push 0 side-effects) 0)
+               (return-3 () (push 3 side-effects) 3))
+          (for (i (return-0) (return-3))
+            (push i result)))
+        (assert-equal '(0 1 2 3) (nreverse result))
+        (assert-equal '(0 3) (nreverse side-effects)))))
+
+;; (do* ((a (return-0))
+;;      (b (return-3))
+;;      (i a (1+ i)))
+;;     ((> i b))
+;;   (push i result))
+;;
+;; so, my mistake was: using DO and trying to cross reference temp vars
+;; and mistyping 1+ as 1_

lisp-koans/koans/triangle-project.lisp

@@ -14,15 +14,28 @@
 
 (define-condition triangle-error (error)
   ;; Fill in the blank with a suitable slot definition.
-  (____))
+  ((triangle-error-sides :initarg :sides :reader triangle-error-sides)))
 
 (defun triangle (a b c)
   ;; Fill in the blank with a function that satisfies the below tests.
-  ____)
+  (cond
+    ((or (<= a 0) (<= b 0) (<= c 0)) (signal (make-condition 'type-error
+                                                      :datum (car (remove-if-not (lambda (n) (>= 0 n)) (list a b c)))
+                                                      :expected-type '(real (0)))))
+    ((or (<= (+ a b) c) (<= (+ b c) a) (<= (+ a c) b)) (signal (make-condition 'triangle-error
+                                                                               :sides (list a b c))))
+    ((= a b c) :equilateral)
+    ((or (= a b) (= b c) (= a c)) :isosceles)
+    (t :scalene)))
+
+(car (remove-if (lambda (n) (>= 0 n)) (list 1 2 -2)))
+
+(triangle 1 1 1)
+(triangle 0 0 0)
 
 (define-test equilateral-triangles
-  ;; Equilateral triangles have three sides of equal length,
+    ;; Equilateral triangles have three sides of equal length,
-  (assert-equal :equilateral (triangle 2 2 2))
+    (assert-equal :equilateral (triangle 2 2 2))
   (assert-equal :equilateral (triangle 10 10 10)))
 
 (define-test isosceles-triangles
@@ -39,27 +52,39 @@
   (assert-equal :scalene (triangle 10 11 12))
   (assert-equal :scalene (triangle 5 4 2)))
 
-(define-test illegal-triangles
+(defun triangle-failure (a b c)
-  ;; Not all triplets make valid triangles.
-  (flet ((triangle-failure (a b c)
            (handler-case (progn (triangle a b c) (error "Test failure"))
-             (error (condition) condition))))
+             (error (condition) condition)))
-    (let ((condition (triangle-failure 0 0 0)))
+(triangle 0 0 0)
-      (assert-true (typep condition 'type-error))
+(setq condi (triangle-failure 2 -1 1))
-      (assert-equal 0 (type-error-datum condition))
+(type-error-datum condi)
-      ;; The type (REAL (0)) represents all positive numbers.
+(type-error-expected-type condi)
-      (assert-true (subtypep (type-error-expected-type condition) '(real (0))))
+
-      ;; If two type specifiers are SUBTYPEP of one another, then they represent
+(setq condi (triangle-failure 2 4 2))
-      ;; the same Lisp type.
+(triangle-error-sides condi)
-      (assert-true (subtypep '(real (0)) (type-error-expected-type condition))))
+
-    (let ((condition (triangle-failure 3 4 -5)))
+
-      (assert-true (typep condition 'type-error))
+(define-test illegal-triangles
-      (assert-equal -5 (type-error-datum condition))
+    ;; Not all triplets make valid triangles.
-      (assert-true (subtypep (type-error-expected-type condition) '(real (0))))
+    (flet ((triangle-failure (a b c)
-      (assert-true (subtypep '(real (0)) (type-error-expected-type condition))))
+             (handler-case (progn (triangle a b c) (error "Test failure"))
-    (let ((condition (triangle-failure 1 1 3)))
+               (error (condition) condition))))
-      (assert-true (typep condition 'triangle-error))
+      (let ((condition (triangle-failure 0 0 0)))
-      (assert-equal '(1 1 3) (triangle-error-sides condition)))
+        (assert-true (typep condition 'type-error))
-    (let ((condition (triangle-failure 2 4 2)))
+        (assert-equal 0 (type-error-datum condition))
-      (assert-true (typep condition 'triangle-error))
+        ;; The type (REAL (0)) represents all positive numbers.
-      (assert-equal '(2 4 2) (triangle-error-sides condition)))))
+        (assert-true (subtypep (type-error-expected-type condition) '(real (0))))
+        ;; If two type specifiers are SUBTYPEP of one another, then they represent
+        ;; the same Lisp type.
+        (assert-true (subtypep '(real (0)) (type-error-expected-type condition))))
+      (let ((condition (triangle-failure 3 4 -5)))
+        (assert-true (typep condition 'type-error))
+        (assert-equal -5 (type-error-datum condition))
+        (assert-true (subtypep (type-error-expected-type condition) '(real (0))))
+        (assert-true (subtypep '(real (0)) (type-error-expected-type condition))))
+      (let ((condition (triangle-failure 1 1 3)))
+        (assert-true (typep condition 'triangle-error))
+        (assert-equal '(1 1 3) (triangle-error-sides condition)))
+      (let ((condition (triangle-failure 2 4 2)))
+        (assert-true (typep condition 'triangle-error))
+        (assert-equal '(2 4 2) (triangle-error-sides condition)))))