diff --git a/Makefile b/Makefile
index e95bc05..a5dd923 100644
--- a/Makefile
+++ b/Makefile
@@ -14,6 +14,10 @@ $(BINARY): $(CFILES) $(LEXER_C) $(LEXER_H)
 	mkdir -p bin
 	gcc -O3 -o $(BINARY) $(CFILES) -lm -Wall -Wextra -Wno-unused-function
 
+debug: $(CFILES) $(LEXER_C) $(LEXER_H)
+	mkdir -p bin
+	gcc -g -O0 -o $(BINARY) $(CFILES) -lm -Wall -Wextra -Wno-unused-function
+
 clean:
 	rm -rf bin
 	rm -f $(LEXER_C) $(LEXER_H)
\ No newline at end of file
diff --git a/src/lexer/lex.l b/src/lexer/lex.l
index 166168d..5285df5 100644
--- a/src/lexer/lex.l
+++ b/src/lexer/lex.l
@@ -1,9 +1,14 @@
+%option reentrant
+
 %{
 #include "token.h"
-int current_line = 1;
-int current_column = 1;
+#include "lexer.h"
+#define GET_STATE LexerState *state = (LexerState *)yyget_extra(yyscanner);
+#define GET_ADD_COLUMN COLUMN_NO += yyleng;
+#define LINE_NO yylineno+1
+#define COLUMN_NO state->current_column
 
-int yywrap() {
+int yywrap(void *) {
     return 1;
 }
 %}
@@ -11,37 +16,43 @@ int yywrap() {
 %%
 
 \"(\\[a-z\"'`]|[^\\"])*\" {
-    add_token(TOKEN_STRING, yytext, current_line, current_column);
-    current_column += yyleng;
+    GET_STATE
+    add_token(TOKEN_STRING, yytext, LINE_NO, COLUMN_NO);
+    GET_ADD_COLUMN
 }
 
 [0-9]+ {
-    add_token(TOKEN_NUMBER, yytext, current_line, current_column);
-    current_column += yyleng;
+    GET_STATE
+    add_token(TOKEN_NUMBER, yytext, LINE_NO, COLUMN_NO);
+    GET_ADD_COLUMN
 }
 
 [a-zA-Z_][a-zA-Z0-9_]* {
-    add_token(TOKEN_IDENTIFIER, yytext, current_line, current_column);
-    current_column += yyleng;
+    GET_STATE
+    add_token(TOKEN_IDENTIFIER, yytext, LINE_NO, COLUMN_NO);
+    GET_ADD_COLUMN
 }
 
 "." {
-    add_token(TOKEN_DOT, yytext, current_line, current_column);
-    current_column += yyleng;
+    GET_STATE
+    add_token(TOKEN_DOT, yytext, LINE_NO, COLUMN_NO);
+    GET_ADD_COLUMN
 }
 
 \n {
-    add_token(TOKEN_NEW_LINE, yytext, current_line, current_column);
-    current_line++;
-    current_column = 1;
+    GET_STATE
+    add_token(TOKEN_NEW_LINE, yytext, LINE_NO, COLUMN_NO);
+    COLUMN_NO = 1;
 }
 
 [ \t]+ {
-    current_column += yyleng;  // Advance column for whitespace
+    GET_STATE
+    GET_ADD_COLUMN  // Advance column for whitespace
 }
 
-.   { 
-    fprintf(stderr, "Error: Unexpected character '%c' at line %d\n", *yytext, yylineno);
+.   {
+    GET_STATE
+    fprintf(stderr, "Error in file %s on line %d column %d: unexpected character '%s'\n", state->filename, LINE_NO, COLUMN_NO, yytext);
     exit(1);
 }
 %%
\ No newline at end of file
diff --git a/src/lexer/lexer.c b/src/lexer/lexer.c
index 38bc85c..58eef98 100644
--- a/src/lexer/lexer.c
+++ b/src/lexer/lexer.c
@@ -1,16 +1,27 @@
 #include "lex.yy.h"
 #include "token.h"
+#include "lexer.h"
 
 int lexer() {
-    const char *input = "term.log\n";
+    yyscan_t scanner;
+    LexerState state = { "file1.src", 1 };
 
+    const char *input = "let x = 10";
 
+    yylex_init(&scanner);
 
-    void* buffer = yy_scan_string(input);
-    yy_switch_to_buffer(buffer);
-    yylex();  // This fills the token array
-    yy_delete_buffer(buffer);
+    // Set the extra data *before* scanning
+    yyset_extra(&state, scanner);
 
+    void* buffer = yy_scan_string(input, scanner);
+    yy_switch_to_buffer(buffer, scanner);
+
+    yylex(scanner);  // This fills the token array
+
+    yy_delete_buffer(buffer, scanner);
+    yylex_destroy(scanner);
+
+    // print tokens etc.
     for (int i = 0; i < token_count; i++) {
         printf("Token(type=%d, value='%s')\n", tokens[i].type, tokens[i].value);
     }
diff --git a/src/lexer/lexer.h b/src/lexer/lexer.h
index c03af10..5646f0e 100644
--- a/src/lexer/lexer.h
+++ b/src/lexer/lexer.h
@@ -1 +1,7 @@
-int lexer();
\ No newline at end of file
+typedef struct {
+    const char *filename;
+    int current_column;
+    // add more fields as needed
+} LexerState;
+
+int lexer();
diff --git a/src/main.c b/src/main.c
index 7e0f830..4705d7e 100644
--- a/src/main.c
+++ b/src/main.c
@@ -1,9 +1,4 @@
-#include "string/string.h"
 #include "number/number.h"
-
-#include <stdio.h>
-#include <stdlib.h>
-#include <string.h>
 #include "lexer/lexer.h"
 
 void initialize() {