diff --git a/assignment2-starter/README.md b/assignment2-starter/README.md
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+# assignment2-starter
+
+Starter code for Assignment 2.
\ No newline at end of file
diff --git a/assignment2-starter/collaborations.txt b/assignment2-starter/collaborations.txt
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+I did not consulted with anyone outside of class for this particular assignment.
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diff --git a/assignment2-starter/factorial.scm b/assignment2-starter/factorial.scm
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+++ b/assignment2-starter/factorial.scm
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+(define fact
+  (lambda (n)
+    (if (equal? n 1)
+        1
+        (* n (fact (- n 1))))))
+
+,tr (fact 5)
+
diff --git a/assignment2-starter/main.scm b/assignment2-starter/main.scm
new file mode 100755
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+++ b/assignment2-starter/main.scm
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+; Written by Thien K. M Bui 
+; Last updated 01/09/2022
+; HW02 CS251 Winter 2022
+
+; sum 
+; param: list of integers 
+; return: sum of all integers in list 
+
+(define sum 
+    (lambda (currentList)
+        (if (equal? (length currentList) 0)
+            0 
+            (+ (car currentList) (sum (cdr currentList))))))
+
+; keep-first-n 
+; param: list of items, integer n 
+; return: items in list up to n provided index, 
+;     if n is 0, bigger than length of list, or negative, return empty list 
+
+(define keep-first-n 
+    (lambda (index currentList)
+        (cond 
+            ((<= index 0) '())
+            ((> index (length currentList)) '())
+            (else (cons (car currentList) (keep-first-n (- index 1) (cdr currentList)))))))
+
+
+
+
+
+
+
+
diff --git a/assignment2-starter/scheme b/assignment2-starter/scheme
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--- /dev/null
+++ b/assignment2-starter/scheme
@@ -0,0 +1,2 @@
+export GUILE_AUTO_COMPILE=0
+rlwrap guile "$@"
diff --git a/assignment2-starter/test-m b/assignment2-starter/test-m
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index 0000000..6061803
--- /dev/null
+++ b/assignment2-starter/test-m
@@ -0,0 +1 @@
+./scheme tester-script.scm "tests-m.scm"
diff --git a/assignment2-starter/tester-script.scm b/assignment2-starter/tester-script.scm
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+++ b/assignment2-starter/tester-script.scm
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+;; Based on https://srfi.schemers.org/srfi-64/srfi-64.html Unit testing set up
+;; code below. Ignore most of this; the important part to focus on is the tests
+;; in the associated files.
+(use-modules (ice-9 format))
+(use-modules (srfi srfi-64))
+(define (my-simple-runner)
+  (let ((runner (test-runner-null))
+        (num-passed 0)
+        (num-failed 0))
+    (test-runner-on-test-end! runner
+      (lambda (runner)
+        (case (test-result-kind runner)
+          ((pass xpass) (set! num-passed (+ num-passed 1)))
+          ((fail xfail)
+           (format #t "FAILED:\n   ~s:line ~s\n   ~s\n"
+                   (test-result-ref runner 'source-file)
+                   (test-result-ref runner 'source-line)
+                   (test-result-ref runner 'source-form))
+
+           (set! num-failed (+ num-failed 1)))
+          (else #t))))
+    (test-runner-on-final! runner
+      (lambda (runner)
+        (format #t "Passing tests: ~d.~%Failing tests: ~d.~%"
+                num-passed num-failed)))
+    runner))
+
+(load "main.scm")
+
+(test-runner-factory
+ (lambda () (my-simple-runner)))
+
+(define test-file-name (cadr (command-line)))
+
+(test-begin "test suite")
+(load test-file-name)
+(test-end "m test suite")
+
+(exit (test-runner-fail-count (test-runner-current)))
diff --git a/assignment2-starter/tests-m.scm b/assignment2-starter/tests-m.scm
new file mode 100755
index 0000000..b589b21
--- /dev/null
+++ b/assignment2-starter/tests-m.scm
@@ -0,0 +1,30 @@
+;; Do not change these tests! We will be using the 
+;; original files to grade, so changing the tests will
+;; only make your own preliminary testing inaccurate.
+
+;; Module to include testing code
+(use-modules (srfi srfi-64))
+
+;; Basic tests for sum
+(test-equal 10 (sum '(4 5 0 1)))
+(test-equal 5 (sum '(4 5 0 1 -2 -3)))
+(test-equal 3 (sum '(3)))
+
+;; Basic tests for keep-first-n
+(test-equal '(a b c) (keep-first-n 3 '(a b c d e)))
+(test-equal '(a b) (keep-first-n 2 '(a b c d e)))
+(test-equal '(a b c d e) (keep-first-n 5 '(a b c d e)))
+(test-equal '(a) (keep-first-n 1 '(a b c d e)))
+(test-equal '(d) (keep-first-n 1 '(d)))
+
+;; Advanced test for sum (assignment specifies that 0
+;; should be returned for the empty list)
+(test-equal 0 (sum '()))
+
+
+;; Advanced tests for keep-first-n (assignment specifies 
+;; that the empty list should be returned when n is 
+;; negative or larger than the length of the input list)
+(test-equal '() (keep-first-n 6 '(a b c d e)))
+(test-equal '() (keep-first-n -1 '(a b c d e)))
+(test-equal '() (keep-first-n 0 '(a b c)))
diff --git a/assignment3-starter/main.scm b/assignment3-starter/main.scm
new file mode 100644
index 0000000..9a6d0b5
--- /dev/null
+++ b/assignment3-starter/main.scm
@@ -0,0 +1,77 @@
+;Written by Thien K. M. Bui
+; Last modified 01/11/2022
+; HW03 CS251 Winter 2022, bst assignment
+
+; entry
+; param bst  
+; return the root node of provided bst 
+(define entry 
+    (lambda (bst)
+        (cond 
+            ;if not a list, return #f
+            ((not (list? bst)) #f)
+            ((not (= (length bst) 3)) #f)
+            ;check the 2nd element
+            ((not (list? (car (cdr bst)))) #f)
+            ;check the 3rd element of a list 
+            ((not (list? (car (cdr (cdr bst))))) #f)
+            (else (car bst)))))
+
+;left 
+;param bst
+; return left subtree of provided bst
+(define left 
+    (lambda (bst)
+        (cond 
+            ((not (list? bst)) #f)
+            ((not (= (length bst) 3)) #f)
+            ;check the 2nd element
+            ((not (list? (car (cdr bst)))) #f)
+            ;check the 3rd element of a list 
+            ((not (list? (car (cdr (cdr bst))))) #f)
+            (else (car (cdr bst))))))
+
+;right
+;param bst
+;return the right subtree of provided bst
+(define right 
+    (lambda (bst)
+        (cond 
+            ((not (list? bst)) #f)
+            ((not (= (length bst) 3)) #f)
+            ;check the 2nd element
+            ((not (list? (car (cdr bst)))) #f)
+            ;check the 3rd element of a list 
+            ((not (list? (car (cdr (cdr bst))))) #f)
+            (else (car (cdr (cdr bst)))))))
+
+;make-bst 
+; param: root node, left-bst, right-bst
+; return new tree whose node is elt, left subtree is left-bst, right subtree is right-bst
+(define make-bst
+    (lambda (elt left-bst right-bst) 
+        (cond 
+            ;if elt is bad
+            ( (not (integer? elt)) #f)
+            ;if left-bst is bad (not of length 3 and 0 or not a list)
+            ( (or (and (not (= (length left-bst) 0)) (not (= (length left-bst) 3))) (not (list? left-bst))) #f)
+            ;if right-bst is bad
+            ( (or (and (not (= (length right-bst) 0)) (not (= (length right-bst) 3))) (not (list? right-bst))) #f)   
+            (else  (list elt left-bst right-bst)))))
+
+;pre-order
+; param: bst
+; return all nodes within bst in pre-order 
+(define preorder
+    (lambda (bst)
+        ;return bst
+        ;make list of pre-order(left-subtree)
+        ;make list of pre-order(right-subtree)
+
+        ;use cons
+        (if (null? bst)
+            '()
+            (append (entry bst) (preorder (left bst)) (preorder (right bst))))))
+
+            
+; (preorder '(1 (2 () ()) (3 () ())))
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diff --git a/assignment3-starter/scheme b/assignment3-starter/scheme
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index 0000000..22d0024
--- /dev/null
+++ b/assignment3-starter/scheme
@@ -0,0 +1,2 @@
+export GUILE_AUTO_COMPILE=0
+rlwrap guile "$@"
\ No newline at end of file
diff --git a/assignment3-starter/test-m b/assignment3-starter/test-m
new file mode 100755
index 0000000..64ceacb
--- /dev/null
+++ b/assignment3-starter/test-m
@@ -0,0 +1 @@
+./scheme tester-script.scm "tests-m.scm"
\ No newline at end of file
diff --git a/assignment3-starter/tester-script.scm b/assignment3-starter/tester-script.scm
new file mode 100644
index 0000000..46c9162
--- /dev/null
+++ b/assignment3-starter/tester-script.scm
@@ -0,0 +1,39 @@
+;; Based on https://srfi.schemers.org/srfi-64/srfi-64.html Unit testing set up
+;; code below. Ignore most of this; the important part to focus on is the tests
+;; in the associated files.
+(use-modules (ice-9 format))
+(use-modules (srfi srfi-64))
+(define (my-simple-runner)
+  (let ((runner (test-runner-null))
+        (num-passed 0)
+        (num-failed 0))
+    (test-runner-on-test-end! runner
+      (lambda (runner)
+        (case (test-result-kind runner)
+          ((pass xpass) (set! num-passed (+ num-passed 1)))
+          ((fail xfail)
+           (format #t "FAILED:\n   ~s:line ~s\n   ~s\n"
+                   (test-result-ref runner 'source-file)
+                   (test-result-ref runner 'source-line)
+                   (test-result-ref runner 'source-form))
+
+           (set! num-failed (+ num-failed 1)))
+          (else #t))))
+    (test-runner-on-final! runner
+      (lambda (runner)
+        (format #t "Passing tests: ~d.~%Failing tests: ~d.~%"
+                num-passed num-failed)))
+    runner))
+
+(load "main.scm")
+
+(test-runner-factory
+ (lambda () (my-simple-runner)))
+
+(define test-file-name (cadr (command-line)))
+
+(test-begin "test suite")
+(load test-file-name)
+(test-end "m test suite")
+
+(exit (test-runner-fail-count (test-runner-current)))
diff --git a/assignment3-starter/tests-m.scm b/assignment3-starter/tests-m.scm
new file mode 100644
index 0000000..7dd1087
--- /dev/null
+++ b/assignment3-starter/tests-m.scm
@@ -0,0 +1,84 @@
+;; DO NOT CHANGE THESE TESTS.
+
+;; Module to include testing code
+(use-modules (srfi srfi-64))
+
+;; Basic tests for entry, left, right
+(test-equal 1
+             (entry '(1 () ())))
+(test-equal '(2 () ())
+             (left '(1 (2 () ()) (3 () ()))))
+(test-equal '(3 () ())
+             (right '(1 (2 () ()) (3 () ()))))
+
+;; Basic tests for make-bst
+(test-equal '(3 () ())
+             (make-bst 3 '() '()))
+
+(test-equal '(3 (1 () (2 () ())) (6 (4 () ()) (18 () ())))
+             (make-bst 3 '(1 () (2 () ())) '(6 (4 () ()) (18 () ()))))
+
+;; Basci test for orderings
+(test-equal '(1 2 3)
+             (preorder '(1 (2 () ()) (3 () ()))))
+
+(let ((test-tree '(8 (4 () (6 () (7 () ())))
+                    (28 (22 () (23 () ())) ()))))
+ (test-equal  '(8 4 6 7 28 22 23)
+               (preorder test-tree))
+ )
+
+ (test-equal '(2 1 3)
+   (inorder '(1 (2 () ()) (3 () ()))))
+
+ (test-equal '(2 3 1)
+   (postorder '(1 (2 () ()) (3 () ()))))
+
+;; Basic tests for insert
+(test-equal '(5 () ())
+             (insert 5 '()) )
+(test-equal  '(6 (5 () ()) ())
+              (insert 5 '(6 () ())))
+(test-equal  '(4 () (5 () ()))
+              (insert 5 '(4 () ())))
+(test-equal '(8 (4 () (6 () (7 () ()))) (28 (22 (10 () ()) (23 () ())) ()))
+             (insert 10 '(8 (4 () (6 () (7 () ()))) (28 (22 () (23 () ())) ()))))
+
+ ;; Advanced tests for orderings
+(let ((test-tree '(8 (4 () (6 () (7 () ())))
+                     (28 (22 () (23 () ())) ()))))
+  (test-equal '(4 6 7 8 22 23 28)
+    (inorder test-tree))
+  (test-equal '(7 6 4 23 22 28 8)
+    (postorder test-tree) )
+  )
+
+ ;; Advanced tests for entry, left, right (edge cases)
+ (test-assert (not (entry '(a b c))))
+ (test-assert (not (left '(a b c))))
+ (test-assert (not (right '(a b c))))
+ (test-assert (not (entry '())))
+ (test-assert (not (left '())))
+ (test-assert (not (right '())))
+
+ ;; Advanced tests for make-bst (edge cases)
+ (test-assert (not (make-bst 1 2 3)))
+ (test-assert (not (make-bst 1.5 '() '())))
+ (test-assert (not (make-bst 'a '() '())))
+ (test-assert (not (make-bst 1 '(2) '())))
+ (test-assert (not (make-bst 1 '() '(3))))
+ (test-assert (not (make-bst 1 '(5 6 7) '(2 3 4))))
+
+;; Advanced tests for orderings (edge cases)
+ (test-equal '(1)
+   (preorder '(1 () ())))
+ (test-equal '(1)
+   (inorder '(1 () ())))
+ (test-equal '(1)
+   (postorder '(1 () ())))
+ (test-equal '()
+   (preorder '()))
+ (test-equal '()
+   (inorder '()))
+ (test-equal '()
+   (postorder '()))