diff --git a/twasm/asm/main.asm b/twasm/asm/main.asm
index 1402364..9805b56 100644
--- a/twasm/asm/main.asm
+++ b/twasm/asm/main.asm
@@ -9,13 +9,17 @@ TEST_ARENA_SIZE equ 0x1000     ; maximum size tests can use
 OUTPUT_ADDR equ 0x00070000 ; address of outputed binary
 OUTPUT_SIZE equ 0x1000     ; max length of outputed binary
 
+STACK_ADDR equ 0x00060000 ; address to put the 64-bit stack at
+
 [bits 64]
 [org LOAD_ADDR]
 
 start:
+  mov rsp, STACK_ADDR ; we might need more stack space, let's just be safe
+
   mov rsi, msg_welcome
   call print
- 
+
   call run_tests
 
   jmp halt
@@ -41,21 +45,35 @@ start:
 
 copy_token:
   .loop:
-    mov al, [rdi] ; check if next char is a space
-    cmp al, " "
-    je .break
 
-    call copy_byte ; copy the next byte if not
+    mov dl, [rdi] ; move bit to compare to current byte in read buffer
 
-    inc rdi ; increment read- and write-pointers
-    inc rsi
-    jmp .loop ; and loop again
+    push rdi ; push incrementors to call elemb
+    push rsi ;
+
+    mov rdi, 8                  ; length of terminator list
+    mov rsi, token_terminator_8 ; start of terminator list
+                                ; dl set before pushing rdi
+    call elemb
+
+    pop rsi ;
+    pop rdi ; pop incrementors after call
+
+    cmp rax, 1 ; check if the next character is a token terminator
+    je .break  ; > if so, break the function
+
+    ; rdi and rsi set from previous loop iteration
+    call copy_byte ; if not, copy the current byte in read buffer
+
+    inc rdi ; read pointer
+    inc rsi ; write pointer
+
+    jmp .loop
 
   .break:
-    mov rax, rdi ; return values
-    mov rdx, rsi
+    mov rax, rdi ; -> last byte read
+    mov rdx, rsi ; -> last byte written
     ret
-  .msg db "yo loop copy_token", 0x0D, 0x0A, 0x00
     
 ; ------------------------------------------------------------------------------
 ; copy_byte
@@ -118,6 +136,48 @@ halt:
   hlt
   jmp halt
 
+; ------------------------------------------------------------------------------
+; elemb
+;
+; description:
+; checks if given byte is element of the specified list
+;
+; parameters:
+; rdi = size of list
+; rsi -> start of list
+; dl =  given byte
+;
+; returned:
+; rax = 0: is not an element
+;       1: is an element
+; ------------------------------------------------------------------------------
+
+elemb:
+  .loop
+    cmp rdi, 0    ; check if remaining length 0
+    je .not_found ; if so, break; dl not an element of list
+
+    mov al, [rsi]
+    cmp al, dl    ; check if current byte in list is the desired byte
+    je .found     ; if so, break; dl an element of list
+
+    inc rsi ; move to next byte
+    dec rdi ; and reduce remaining length
+
+    jmp .loop
+
+  .not_found
+    xor rax, rax ; return 0; dl not an element of list
+    ret
+
+  .found
+    xor rax, rax
+    mov rax, 1 ; return 1; dl an element of list
+    ret
+
+  .f db "found", 0x0D, 0x0A, 0x00
+  .nf db "not found", 0x0D, 0x0A, 0x00
+
 ; ------------------------------------------------------------------------------
 ; tests
 ; ------------------------------------------------------------------------------
@@ -135,6 +195,7 @@ run_tests:
 
   call test_copy_byte
   call test_copy_token
+  call test_elemb
 
   ret
   .msg db "running test suite...", 0x0D, 0x0A, 0x00
@@ -143,7 +204,7 @@ run_tests:
 ; test_copy_byte
 ;
 ; description:
-; tests copy_byte's described functionality
+; tests copy_byte described functionality
 ; ------------------------------------------------------------------------------
 
 test_copy_byte:
@@ -183,20 +244,39 @@ test_copy_token:
   mov rsi, .msg
   call print
 
-  mov rdi, test_token      ; read buffer
-  mov rsi, TEST_ARENA_ADDR ; write buffer
+  ; test case: space terminated
+
+  mov rdi, test_token_space ; read buffer
+  mov rsi, TEST_ARENA_ADDR  ; write buffer
   call copy_token
 
   ; check reported final indicies with the expected final indicies
-  cmp rax, test_token + 8 ; last byte read
+  cmp rax, test_token_space + 8 ; last byte read
   jne .fail
   cmp rdx, TEST_ARENA_ADDR + 8 ; last byte written
   jne .fail
 
   mov rsi, TEST_ARENA_ADDR
   mov rcx, [rsi]
-  cmp rcx, [test_token] ; compare copied token to expected token
+  cmp rcx, [test_token_space] ; check if copied token matches expected token
+  jne .fail                   ; if not, fail
+
+  ; test case: null terminated
+
+  mov rdi, test_token_null ; read buffer
+  mov rsi, TEST_ARENA_ADDR ; write buffer
+  call copy_token
+
+  ; check reported final indicies with the expected final indicies
+  cmp rax, test_token_null + 8 ; last byte read
   jne .fail
+  cmp rdx, TEST_ARENA_ADDR + 8 ; last byte written
+  jne .fail
+
+  mov rsi, TEST_ARENA_ADDR
+  mov rcx, [rsi]
+  cmp rcx, [test_token_null] ; check if copied token matches expected token
+  jne .fail                  ; if not, fail
 
   .pass:
     mov rsi, msg_pass
@@ -208,6 +288,67 @@ test_copy_token:
     ret
   .msg db "test_copy_token...", 0x00
 
+; ------------------------------------------------------------------------------
+; test_elemb
+;
+; description:
+; tests elemb described functionality
+; ------------------------------------------------------------------------------
+
+test_elemb:
+  mov rsi, .msg
+  call print
+
+  ; [0]
+  mov rdi, 5
+  mov rsi, test_elemb_5
+  mov dl, [test_elemb_5]
+  call elemb
+  cmp al, 1
+  jne .fail
+
+  ; [n - 1]
+  mov rdi, 5
+  mov rsi, test_elemb_5
+  mov dl, [test_elemb_5 + 4]
+  call elemb
+  cmp al, 1
+  jne .fail
+
+  ; [1]
+  mov rdi, 5
+  mov rsi, test_elemb_5
+  mov dl, [test_elemb_5 + 1]
+  call elemb
+  cmp al, 1
+  jne .fail
+
+  ; not present
+  mov rdi, 5
+  mov rsi, test_elemb_5
+  mov dl, 0xDA
+  call elemb
+  cmp al, 0
+  jne .fail
+
+  ; 0 length list
+  mov rdi, 0
+  mov rsi, test_elemb_0
+  mov dl, 0x34
+  call elemb
+  cmp al, 0
+  jne .fail
+
+  .pass:
+    mov rsi, msg_pass
+    call print
+    ret
+  .fail:
+    mov rsi, msg_fail
+    call print
+    ret
+  .msg db "test_elemb...", 0x00
+
 ; ------------------------------------------------------------------------------
 ; data
 ; ------------------------------------------------------------------------------
@@ -217,5 +358,12 @@ msg_halt db "halted.", 0x0D, 0x0A, 0x00
 msg_pass db "passed.", 0x0D, 0x0A, 0x00
 msg_fail db "failed.", 0x0D, 0x0A, 0x00
 
-test_byte db "T"
-test_token db "TestTokn " ; followed by space. Quad word
+test_byte db "Q" ; unterminated, just a byte chillin
+test_token_null db "TestTokn", 0x00 ; followed by null terminator. Quad word
+test_token_space db "TestTokn " ; followed by space. Quad word
+test_elemb_0
+test_elemb_5 db 0x54, 0x00, 0x21, 0x20, 0x34
+
+token_terminator_8 db 0x00, " ", 0x0A, 0x0D, 0x00, 0x00, 0x00, 0x00
+
+debug_string db "debug_string", 0x0D, 0x0A, 0x00