diff --git a/include/lexer.h b/include/lexer.h
index d87441c..eccf1dc 100644
--- a/include/lexer.h
+++ b/include/lexer.h
@@ -34,6 +34,7 @@ typedef enum {
     LEXER_EMPTY_INPUT,
     LEXER_NULL_ARG,
     LEXER_WRONG_SYNTAX,
+    LEXER_BUF_OVERFLOW,
 } LexerErr;
 
 // Can be thought as tokens, they will be used by the parser.
@@ -68,6 +69,7 @@ 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_number(const char* str, double *number);
+LexerErr string_to_number(const char* input, size_t *offset, double *number);
+void reverser_string(char* input);
 
 #endif // !LEXER_H
diff --git a/src/lexer.c b/src/lexer.c
index 859ff93..b0abbb8 100644
--- a/src/lexer.c
+++ b/src/lexer.c
@@ -1,6 +1,10 @@
 #include "lexer.h"
+#include <ctype.h>
+#include <math.h>
+#include <stdint.h>
 #include <stdlib.h>
 #include <strings.h>
+#include <limits.h>
 
 #define NODE_ARRAY_DEFAULT_SIZE 64
 // Helps  state machine for the lexer :)
@@ -78,6 +82,16 @@ ASTNodeArrayErr ASTNodeArray_pop(ASTNodeArray *arr, size_t index, ASTNode *out)
     if (index >= arr->len) {
         return ARRAY_OUT_OF_BOUNDS;
     }
+
+    if (arr->cap / 4 > arr->len) {
+        size_t new_cap = arr->cap / 2;
+        ASTNode *tmp = realloc(arr->data, new_cap * sizeof(ASTNode));
+        if (tmp == NULL) {
+            return ARRAY_ALLOC;
+        }
+        arr->data = tmp;
+        arr->cap = new_cap;
+    }
     
     if (out != NULL) {
         ASTNode node_to_delete = arr->data[index];
@@ -97,3 +111,40 @@ size_t ASTNodeArray_len(ASTNodeArray *arr) {
     }
     return arr->len;
 }
+
+// CURRENTLY, it only supports ints, not clear how floating
+// point is implemented but i'll figure it out
+LexerErr string_to_number(const char *input, size_t *offset, double *number) {
+    char buf[128] = { '\0' };
+    size_t buf_pos = 0;
+
+    size_t current = *offset;
+    while (isdigit(input[current])) {
+        buf[buf_pos] = input[current];
+        
+        if (buf_pos >= sizeof(buf)) {
+            return LEXER_BUF_OVERFLOW;
+        }
+        current++;
+        buf_pos++;
+    }
+    
+    int c = 0;
+    long count = 0;
+    while (buf[c] != '\0') {
+        
+        int digit = buf[c] - '0';
+
+        if (count > (INT_MAX - digit) / 10) {
+            return LEXER_FAILED_NUMBER_CONVERSION;
+        }
+        count = count * 10;
+        count += digit;
+        
+        c++;
+    }
+
+    *number = (double) count;
+    *offset = current;
+    return LEXER_OK;
+}
diff --git a/test/CMakeLists.txt b/test/CMakeLists.txt
index 99aff45..3aad9e4 100644
--- a/test/CMakeLists.txt
+++ b/test/CMakeLists.txt
@@ -1,10 +1,17 @@
 find_package(cmocka REQUIRED)
 
 add_executable(test_nodeArray test_ASTNodeArray.c)
+add_executable(test_lexer test_lexer.c)
 
 target_link_libraries(test_nodeArray
     calculator_lib
     cmocka::cmocka
 )
 
+target_link_libraries(test_lexer
+    calculator_lib
+    cmocka::cmocka
+)
+
 add_test(NAME nodeArray_tests COMMAND test_nodeArray)
+add_test(NAME lexer_tests COMMAND test_lexer)
diff --git a/test/test_ASTNodeArray.c b/test/test_ASTNodeArray.c
index 6d81a97..cc28297 100644
--- a/test/test_ASTNodeArray.c
+++ b/test/test_ASTNodeArray.c
@@ -34,12 +34,15 @@ static void test_array_push(void **state) {
 
     assert_int_equal(ASTNodeArray_push(&arr, node3), ARRAY_OK);
     assert_int_equal(ASTNodeArray_len(&arr), 3);
+
+    ASTNodeArray_free(&arr);
 }
 
 static void test_array_pop(void **state) {
     (void) state;
 
-    ASTNodeArray arr = ASTNodeArray_init(2);
+    // Set to force desize
+    ASTNodeArray arr = ASTNodeArray_init(16);
     ASTNode node1 = {
         .type = NODE_NUMBER,
         .data = { .number = 90 }
@@ -68,8 +71,11 @@ static void test_array_pop(void **state) {
     assert_int_equal(ASTNodeArray_pop(&arr, 1, &node4), ARRAY_OK);
     assert_int_equal(node4.type, NODE_NUMBER);
     assert_int_equal(node4.data.number, 80);
+
+    ASTNodeArray_free(&arr);
 }
 
+
 int main(void) {
     const struct CMUnitTest tests[] = {
         cmocka_unit_test(test_array_push),
diff --git a/test/test_lexer.c b/test/test_lexer.c
new file mode 100644
index 0000000..8d59e72
--- /dev/null
+++ b/test/test_lexer.c
@@ -0,0 +1,27 @@
+#include "lexer.h"
+#include <stdarg.h>
+#include <stdbool.h>
+#include <stddef.h>
+#include <stdint.h>
+#include <setjmp.h>
+#include <cmocka.h>
+
+static void test_string_to_number(void **state) {
+    (void) state;
+
+    char num[16] = "2333t55";
+    size_t offset = 0;
+    double result = 0;
+    assert_int_equal(string_to_number(num, &offset, &result), 0);
+
+    assert_int_equal(offset, 4);
+    assert_double_equal(result, 2333, 1e-6);
+}
+
+int main(void) {
+    const struct CMUnitTest tests[] = {
+        cmocka_unit_test(test_string_to_number),
+    };
+
+    return cmocka_run_group_tests(tests, NULL, NULL);
+}