learning koans

- refreshed understanding of lexical vs. dynamic binding
  https://gigamonkeys.com/book/variables.html
- was taught CASE as simpler variant of COND

lisp-koans/koans/asserts.lisp

@@ -28,38 +28,38 @@
 ;;; Sometimes, you will be asked to provide values that are equal to something.
 
 (define-test fill-in-the-blanks
-  (assert-equal ____ 2)
-  (assert-equal ____ 3.14)
-  (assert-equal ____ "Hello World"))
+  (assert-equal 2 2)
+  (assert-equal 3.14 3.14)
+  (assert-equal "Hello World" "Hello World"))
 
 ;;; Sometimes, you will be asked to say whether something is true or false,
 ;;; In Common Lisp, the canonical values for truth and falsehood are T and NIL.
 
 (define-test assert-true
-  (assert-true ____))
+  (assert-true t))
 
 (define-test assert-false
-  (assert-false ____))
+  (assert-false nil))
 
+;; could use C-x C-e (sly-eval-last-expression) to eval just (= 34 34) to check whether T or NIL returns
 (define-test true-or-false
-  (true-or-false? ____ (= 34 34))
-  (true-or-false? ____ (= 19 78)))
+  (true-or-false? t (= 34 34))
+  (true-or-false? nil (= 19 78)))
 
 ;;; Since T and NIL are symbols, you can type them in lowercase or uppercase;
 ;;; by default, Common Lisp will automatically upcase them upon reading.
 
 (define-test upcase-downcase
   ;; Try inserting a lowercase t here.
-  (assert-equal ____ T)
+  (assert-equal t T)
   ;; Try inserting an uppercase NIL here.
-  (assert-equal ____ nil))
+  (assert-equal NIL nil))
 
 ;;; Sometimes, you will be asked to provide a part of an expression that must be
 ;;; either true or false.
 
 (define-test a-true-assertion
-  (assert-true (= ____ (+ 2 2))))
+  (assert-true (= 4 (+ 2 2))))
 
 (define-test a-false-assertion
-  (assert-false (= ____ (+ 2 2))))
-
+  (assert-false (= 3 (+ 2 2))))