diff --git a/include/lexer.h b/include/lexer.h
index 3995b2e..fcb6529 100644
--- a/include/lexer.h
+++ b/include/lexer.h
@@ -92,9 +92,9 @@ ASTNodeArrayErr ASTNodeArray_pop(ASTNodeArray *arr, size_t index, ASTNode *out);
 size_t ASTNodeArray_len(ASTNodeArray *arr);
 
 // Lexer funtions as well as few functionality
-LexerErr tokenize(const char* input, ASTNodeArray *out);
-LexerErr tokenize_number(const char* input, size_t *offset, ASTNode *out);
-LexerErr string_to_integer(const char buf[], int64_t *number);
+TokenizeResult tokenize(const char* input);
+ASTNodeResult tokenize_number(const char* input, size_t *offset);
+I64Result string_to_integer(const char buf[]);
 bool isoperator(int c);
 Operator char_to_operator(int c);
 char operator_to_char(Operator op);
diff --git a/src/lexer.c b/src/lexer.c
index 4567c7b..8d80264 100644
--- a/src/lexer.c
+++ b/src/lexer.c
@@ -1,5 +1,7 @@
 #include "lexer.h"
+#include "arraylist.h"
 #include <ctype.h>
+#include <stdbool.h>
 #include <stdint.h>
 #include <stdlib.h>
 #include <strings.h>
@@ -11,32 +13,31 @@ typedef enum {
 } LexerState;
 
 
-LexerErr tokenize(const char *input, ASTNodeArray *out) {
+TokenizeResult tokenize(const char *input) {
     size_t offset = 0;
     LexerState state = WAIT_FOR_NUMBER;
-    ASTNodeArray arr = ASTNodeArray_init(0); // 0 defaults to 64
+    ArrayList *arr = arraylist_init(64, sizeof(ASTNode));
 
     while (input[offset] != '\n' && input[offset] != '\0') {
         int current = input[offset];
 
         if (isdigit(current)) {
             if (state != WAIT_FOR_NUMBER) {
-                ASTNodeArray_free(&arr);
-                return LEXER_WRONG_SYNTAX;
+                arraylist_destroy(&arr);
+                return (TokenizeResult) {.is_valid = false, .err = LEXER_WRONG_SYNTAX};
             }
-            ASTNode new_node;
-            LexerErr result = tokenize_number(input, &offset, &new_node);
+            ASTNodeResult result = tokenize_number(input, &offset);
 
-            if (result != LEXER_OK) {
-                ASTNodeArray_free(&arr);
-                return result;
+            if (!result.is_valid) {
+                arraylist_destroy(&arr);
+                return (TokenizeResult) {.is_valid = false, .err = result.err};
             }
 
-            ASTNodeArray_push(&arr, new_node);
+            arraylist_push_back(arr, &result.node);
             state = WAIT_FOR_OPERATOR;
         } else if (isoperator(current)) {
             if (state != WAIT_FOR_OPERATOR) {
-                return LEXER_WRONG_SYNTAX;
+                return (TokenizeResult) {.is_valid = false, .err =LEXER_WRONG_SYNTAX};
             }
             ASTNode new_node = {
                 .type = NODE_BINARY_OP,
@@ -45,24 +46,23 @@ LexerErr tokenize(const char *input, ASTNodeArray *out) {
                 .data.binary.left = NULL,
             };
 
-            ASTNodeArray_push(&arr, new_node);
+            arraylist_push_back(arr, &new_node);
             state = WAIT_FOR_NUMBER;
         } else if (isspace(current)) {
             // Nothing...
         } else {
-            ASTNodeArray_free(&arr);
-            return LEXER_NOT_RECOGNIZED_SYMBOL;
+            arraylist_destroy(&arr);
+            return (TokenizeResult) {.is_valid = false, .err = LEXER_NOT_RECOGNIZED_SYMBOL};
         }
 
         offset++;
     }
 
-    if (arr.len < 1) {
-        return LEXER_EMPTY_INPUT;
+    if (arraylist_size(arr) < 1) {
+        return (TokenizeResult) {.is_valid = false, .err = LEXER_EMPTY_INPUT};
     }
 
-    *out = arr;
-    return LEXER_OK;
+    return (TokenizeResult) {.is_valid = true, .arr = arr};
 }
 
 // CURRENTLY, it only supports ints, not clear how floating