diff --git a/.gitignore b/.gitignore
index 7ad6275..4777691 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1 +1,2 @@
 /.direnv
+/.cache
diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..8c80ca6
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,24 @@
+all: parser.tab.o lex.yy.o node.o main.o
+	gcc ./parser.tab.o ./lex.yy.o ./node.o ./main.o -o program -lfl
+
+main.o: main.c
+	gcc -c main.c
+
+node.o: node.c
+	gcc -c ./node.c
+
+parser.tab.c parser.tab.h: ./parser.y
+	bison -d parser.y
+
+parser.tab.o: ./parser.tab.c
+	gcc -c ./parser.tab.c
+
+lex.yy.o: lex.yy.c
+	gcc -c lex.yy.c
+
+lex.yy.c: ./scanner.l
+	flex scanner.l
+
+.PHONY: clean
+clean:
+	-rm parser.tab.c parser.tab.h parser.tab.o lex.yy.o lex.yy.c program main.o
diff --git a/flake.lock b/flake.lock
index 0b7c20b..4680682 100644
--- a/flake.lock
+++ b/flake.lock
@@ -19,11 +19,11 @@
     },
     "nixpkgs": {
       "locked": {
-        "lastModified": 1742206328,
-        "narHash": "sha256-q+AQ///oMnyyFzzF4H9ShSRENt3Zsx37jTiRkLkXXE0=",
+        "lastModified": 1742707865,
+        "narHash": "sha256-RVQQZy38O3Zb8yoRJhuFgWo/iDIDj0hEdRTVfhOtzRk=",
         "owner": "NixOS",
         "repo": "nixpkgs",
-        "rev": "096478927c360bc18ea80c8274f013709cf7bdcd",
+        "rev": "dd613136ee91f67e5dba3f3f41ac99ae89c5406b",
         "type": "github"
       },
       "original": {
diff --git a/flake.nix b/flake.nix
index 1946716..53f0721 100644
--- a/flake.nix
+++ b/flake.nix
@@ -23,6 +23,8 @@
             flex
             clang-tools
             clang
+            bear
+            neovim
           ];
         };
       }
diff --git a/main.c b/main.c
new file mode 100644
index 0000000..c6831b0
--- /dev/null
+++ b/main.c
@@ -0,0 +1,26 @@
+#include "node.h"
+#include <stdio.h>
+extern int yyparse();
+extern pNode root;
+extern void yyrestart(FILE *);
+extern int errors;
+
+int main(int argc, char **argv) {
+  if (argc > 1) {
+    FILE *f = fopen(argv[1], "r");
+    if (!f) {
+      perror(argv[1]);
+      return 1;
+    }
+    yyrestart(f);
+  }
+  int running_res = 0;
+  do {
+    running_res = 0;
+    running_res = yyparse();
+  } while (running_res);
+  if (!errors) {
+    DFS(root, 0);
+  }
+  return 0;
+}
diff --git a/node.c b/node.c
new file mode 100644
index 0000000..64f24b1
--- /dev/null
+++ b/node.c
@@ -0,0 +1,201 @@
+#include "node.h"
+#include <stdio.h>
+#include <stdlib.h>
+
+pNode newNode(NodeType typ, intptr_t line, intptr_t size, Node **children,
+              ValueUnion value) {
+  pNode node = (pNode)calloc(sizeof(Node), 1);
+  Node **new_children = (Node **)calloc(sizeof(pNode), size);
+  for (int i = 0; i < size; i++) {
+    new_children[i] = children[i];
+  }
+  node->type = typ;
+  node->line = line;
+  node->size = size;
+  node->children = new_children;
+  node->value = value;
+  return node;
+}
+ValueUnion nullValue() {
+  ValueUnion value = {.null = NULL};
+  return value;
+}
+void displayNode(pNode);
+void DFS(pNode node, int level) {
+  if (node == NULL) {
+    return;
+  };
+
+  if (node->line != -1) {
+    if (node->size == 0) {
+      for (int i = 0; i < level; i++)
+        printf("  ");
+      displayNode(node);
+      putchar('\n');
+    } else {
+      for (int i = 0; i < level; i++)
+        printf("  ");
+      displayNode(node);
+      putchar('\n');
+    }
+  }
+
+  for (int i = 0; i < node->size; i++)
+    DFS(node->children[i], level + 1);
+}
+void displayNode(pNode node) {
+  switch (node->type) {
+  case Type_int:
+    printf("TYPE: int");
+    break;
+  case Type_float:
+    printf("TYPE: float");
+    break;
+  case Ident:
+    printf("ID: %s", node->value.id);
+    break;
+  case Integer:
+    printf("INT: %ld", node->value.integer);
+    break;
+  case Float:
+    printf("FLOAT: %lf", node->value.real);
+    break;
+  case Semi:
+    printf("SEMI");
+    break;
+  case Comma:
+    printf("COMMA");
+    break;
+  case Assignop:
+    printf("ASSIGNOP");
+    break;
+  case Plus:
+    printf("PLUS");
+    break;
+  case Minus:
+    printf("MINUS");
+    break;
+  case Times:
+    printf("TIMES");
+    break;
+  case Div:
+    printf("DIV");
+    break;
+  case And:
+    printf("AND");
+    break;
+  case Or:
+    printf("OR");
+    break;
+  case Dot:
+    printf("DOT");
+    break;
+  case Not:
+    printf("NOT");
+    break;
+  case Lp:
+    printf("LP");
+    break;
+  case Rp:
+    printf("RP");
+    break;
+  case Lb:
+    printf("LB");
+    break;
+  case Rb:
+    printf("RB");
+    break;
+  case Lc:
+    printf("LC");
+    break;
+  case Rc:
+    printf("RC");
+    break;
+  case Struct:
+    printf("STRUCT");
+    break;
+  case Return:
+    printf("RETURN");
+    break;
+  case If:
+    printf("IF");
+    break;
+  case Else:
+    printf("ELSE");
+    break;
+  case While:
+    printf("WHILE");
+    break;
+  case Line_comment:
+    printf("LINE_COMMENT");
+    break;
+  case Block_comment:
+    printf("BLOCK_COMMENT");
+    break;
+  case Program:
+    printf("Program (%ld)", node->line);
+    break;
+  case ExtDefList:
+    printf("ExtDefList (%ld)", node->line);
+    break;
+  case ExtDef:
+    printf("ExtDef (%ld)", node->line);
+    break;
+  case ExtDecList:
+    printf("ExtDecList (%ld)", node->line);
+    break;
+  case Specifier:
+    printf("Specifier (%ld)", node->line);
+    break;
+  case StructSpecifier:
+    printf("StructSpecifier (%ld)", node->line);
+    break;
+  case OptTag:
+    printf("OptTag (%ld)", node->line);
+    break;
+  case Tag:
+    printf("Tag (%ld)", node->line);
+    break;
+  case VarDec:
+    printf("VarDec (%ld)", node->line);
+    break;
+  case FunDec:
+    printf("FunDec (%ld)", node->line);
+    break;
+  case VarList:
+    printf("VarList (%ld)", node->line);
+    break;
+  case ParamDec:
+    printf("ParamDec (%ld)", node->line);
+    break;
+  case CompSt:
+    printf("CompSt (%ld)", node->line);
+    break;
+  case StmtList:
+    printf("StmtList (%ld)", node->line);
+    break;
+  case Stmt:
+    printf("Stmt (%ld)", node->line);
+    break;
+  case DefList:
+    printf("DefList (%ld)", node->line);
+    break;
+  case Def:
+    printf("Def (%ld)", node->line);
+    break;
+  case DecList:
+    printf("DecList (%ld)", node->line);
+    break;
+  case Dec:
+    printf("Dec (%ld)", node->line);
+    break;
+  case Exp:
+    printf("Exp (%ld)", node->line);
+    break;
+  case Args:
+    printf("Args (%ld)", node->line);
+    break;
+  default:
+    printf("%d (%ld)", node->type, node->line);
+  }
+}
diff --git a/node.h b/node.h
new file mode 100644
index 0000000..c255921
--- /dev/null
+++ b/node.h
@@ -0,0 +1,74 @@
+#pragma once
+#include <stdint.h>
+
+typedef enum node_kind_t {
+  Semi,
+  Comma,
+  Assignop,
+  Plus,
+  Minus,
+  Times,
+  Div,
+  And,
+  Or,
+  Dot,
+  Not,
+  Lp,
+  Rp,
+  Lb,
+  Rb,
+  Lc,
+  Rc,
+  Struct,
+  Return,
+  If,
+  Else,
+  While,
+  Type_int,
+  Type_float,
+  Integer,
+  Float,
+  Ident,
+  Line_comment,
+  Block_comment,
+  Program,
+  ExtDefList,
+  ExtDef,
+  ExtDecList,
+  Specifier,
+  StructSpecifier,
+  OptTag,
+  Tag,
+  VarDec,
+  FunDec,
+  VarList,
+  ParamDec,
+  CompSt,
+  StmtList,
+  Stmt,
+  DefList,
+  Def,
+  DecList,
+  Dec,
+  Exp,
+  Args
+} NodeType;
+typedef union value {
+  double real;
+  intptr_t integer;
+  char const *id;
+  void *null;
+} ValueUnion;
+typedef struct node {
+  NodeType type;
+  intptr_t line;
+  intptr_t size;
+  struct node **children;
+  union value value;
+} Node;
+
+typedef Node *pNode;
+
+pNode newNode(NodeType, intptr_t, intptr_t, Node **, ValueUnion);
+ValueUnion nullValue();
+void DFS(pNode, int);
diff --git a/node.o b/node.o
new file mode 100644
index 0000000..ad43ffe
Binary files /dev/null and b/node.o differ
diff --git a/parser.y b/parser.y
new file mode 100644
index 0000000..66b6240
--- /dev/null
+++ b/parser.y
@@ -0,0 +1,311 @@
+%{
+	#include <stdio.h>
+	#include "node.h"
+	extern int yylex(void);
+	extern int yylineno;
+	int errors = 0;
+	struct node;
+	void yyerror(char const *);
+	pNode root;
+%}
+
+%define api.value.type {struct node*}
+
+%token INTEGER FLOAT
+%token SEMI COMMA ASSIGNOP PLUS MINUS TIMES DIV AND OR DOT NOT LP RP LB RB LC RC STRUCT RETURN IF ELSE WHILE
+%token TYPE_INT TYPE_FLOAT ID
+%token LINE_COMMENT BLOCK_COMMENT
+
+%%
+
+// High-level Definitions
+Program:
+     	ExtDefList {
+		pNode children[1] = { $1 };
+		$$ = newNode(Program, yylineno, 1, children, nullValue());
+		root = $$;
+	}
+	;
+ExtDefList:
+	ExtDef ExtDefList {
+		pNode children[2] = { $1, $2 };
+		$$ = newNode(ExtDefList, yylineno, 2, children, nullValue());
+	}
+    	| {
+		$$ = newNode(ExtDefList, -1, 0, NULL, nullValue());
+	}
+    	;
+ExtDef:
+      	Specifier ExtDecList SEMI {
+		pNode children[3] = { $1, $2, $3 };
+		$$ = newNode(ExtDef, yylineno, 3, children, nullValue());
+	}
+    	| Specifier SEMI {
+		pNode children[2] = { $1, $2 };
+		$$ = newNode(ExtDef, yylineno, 2, children, nullValue());
+	}
+    	| Specifier FunDec CompSt {
+		pNode children[3] = { $1, $2, $3 };
+		$$ = newNode(ExtDef, yylineno, 3, children, nullValue());
+	}
+    	;
+ExtDecList:
+	VarDec {
+		pNode children[1] = { $1 };
+		$$ = newNode(ExtDecList, yylineno, 1, children, nullValue());
+	}
+    	| VarDec COMMA ExtDecList {
+		pNode children[3] = { $1, $2, $3 };
+		$$ = newNode(ExtDecList, yylineno, 3, children, nullValue());
+	}
+    	;
+
+// Specifiers
+Specifier:
+	TYPE_INT {
+		pNode children[1] = { $1 };
+		$$ = newNode(Specifier, yylineno, 1, children, nullValue());
+	}
+	| TYPE_FLOAT {
+		pNode children[1] = { $1 };
+		$$ = newNode(Specifier, yylineno, 1, children, nullValue());
+	}
+    	| StructSpecifier {
+		pNode children[1] = { $1 };
+		$$ = newNode(Specifier, yylineno, 1, children, nullValue());
+	}
+    	;
+StructSpecifier:
+	STRUCT OptTag LC DefList RC {
+		pNode children[5] = { $1, $2, $3, $4, $5 };
+		$$ = newNode(StructSpecifier, yylineno, 5, children, nullValue());
+	}
+    	| STRUCT Tag {
+		pNode children[2] = { $1, $2 };
+		$$ = newNode(StructSpecifier, yylineno, 2, children, nullValue());
+	}
+    	;
+OptTag:
+   	ID {
+		pNode children[1] = { $1 };
+		$$ = newNode(OptTag, yylineno, 1, children, nullValue());
+	}
+    	| {
+		$$ = newNode(OptTag, -1, 0, NULL, nullValue());
+	}
+    	;   
+Tag:
+   	ID {
+		pNode children[1] = { $1 };
+		$$ = newNode(Tag, yylineno, 1, children, nullValue());
+	}
+    	;
+
+// Declarators
+VarDec:
+   	ID {
+		pNode children[1] = { $1 };
+		$$ = newNode(VarDec, yylineno, 1, children, nullValue());
+	}
+    	| VarDec LB INTEGER RB {
+		pNode children[4] = { $1, $2, $3, $4 };
+		$$ = newNode(VarDec, yylineno, 4, children, nullValue());
+	}
+    	;
+FunDec:
+    	ID LP VarList RP {
+		pNode children[4] = { $1, $2, $3, $4 };
+		$$ = newNode(FunDec, yylineno, 4, children, nullValue());
+	}
+    	| ID LP RP {
+		pNode children[3] = { $1, $2, $3 };
+		$$ = newNode(FunDec, yylineno, 3, children, nullValue());
+	}
+    	;
+VarList:
+       	ParamDec COMMA VarList {
+		pNode children[3] = { $1, $2, $3 };
+		$$ = newNode(VarList, yylineno, 3, children, nullValue());
+	}
+    	| ParamDec {
+		pNode children[1] = { $1 };
+		$$ = newNode(VarList, yylineno, 1, children, nullValue());
+	}
+    	;
+ParamDec:
+	Specifier VarDec {
+		pNode children[1] = { $1 };
+		$$ = newNode(ParamDec, yylineno, 1, children, nullValue());
+	}
+    	;
+
+// Statements
+CompSt:
+    	LC DefList StmtList RC {
+		pNode children[4] = { $1, $2, $3, $4 };
+		$$ = newNode(CompSt, yylineno, 4, children, nullValue());
+	}
+    	;
+StmtList:
+	Stmt StmtList {
+		pNode children[2] = { $1, $2 };
+		$$ = newNode(StmtList, yylineno, 2, children, nullValue());
+	}
+    	| {
+		$$ = newNode(StmtList, -1, 0, NULL, nullValue());
+	}
+    	;
+Stmt:
+    	Exp SEMI {
+		pNode children[2] = { $1, $2 };
+		$$ = newNode(Stmt, yylineno, 2, children, nullValue());
+	}
+    	| CompSt {
+		pNode children[1] = { $1 };
+		$$ = newNode(Stmt, yylineno, 1, children, nullValue());
+	}
+    	| RETURN Exp SEMI {
+		pNode children[3] = { $1, $2, $3 };
+		$$ = newNode(Stmt, yylineno, 3, children, nullValue());
+	}
+    	| IF LP Exp RP Stmt {
+		pNode children[5] = { $1, $2, $3, $4, $5 };
+		$$ = newNode(Stmt, yylineno, 5, children, nullValue());
+	}
+    	| IF LP Exp RP Stmt ELSE Stmt {
+		pNode children[7] = { $1, $2, $3, $4, $5, $6, $7 };
+		$$ = newNode(Stmt, yylineno, 7, children, nullValue());
+	}
+    	| WHILE LP Exp RP Stmt {
+		pNode children[5] = { $1, $2, $3, $4, $5 };
+		$$ = newNode(Stmt, yylineno, 5, children, nullValue());
+	}
+	| error SEMI
+    	;
+
+// Local Definitions
+DefList:
+       	Def DefList {
+		pNode children[2] = { $1, $2 };
+		$$ = newNode(DefList, yylineno, 2, children, nullValue());
+	}
+    	| {
+		$$ = newNode(DefList, -1, 0, NULL, nullValue());
+	}
+    	;
+Def:
+   	Specifier DecList SEMI {
+		pNode children[3] = { $1, $2, $3 };
+		$$ = newNode(Def, yylineno, 3, children, nullValue());
+	}
+    	;
+DecList:
+       	Dec {
+		pNode children[1] = { $1 };
+		$$ = newNode(DecList, yylineno, 1, children, nullValue());
+	}
+    	| Dec COMMA DecList {
+		pNode children[3] = { $1, $2, $3 };
+		$$ = newNode(DecList, yylineno, 3, children, nullValue());
+	}
+    	;
+Dec:
+   	VarDec {
+		pNode children[1] = { $1 };
+		$$ = newNode(Dec, yylineno, 1, children, nullValue());
+	}
+    	| VarDec ASSIGNOP Exp {
+		pNode children[3] = { $1, $2, $3 };
+		$$ = newNode(Dec, yylineno, 3, children, nullValue());
+	}
+    	;
+
+// Expressions
+Exp:
+   	Exp ASSIGNOP Exp {
+		pNode children[3] = { $1, $2, $3 };
+		$$ = newNode(Exp, yylineno, 3, children, nullValue());
+	}
+    	| Exp AND Exp {
+		pNode children[3] = { $1, $2, $3 };
+		$$ = newNode(Exp, yylineno, 3, children, nullValue());
+	}
+    	| Exp OR Exp {
+		pNode children[3] = { $1, $2, $3 };
+		$$ = newNode(Exp, yylineno, 3, children, nullValue());
+	}
+    	| Exp PLUS Exp {
+		pNode children[3] = { $1, $2, $3 };
+		$$ = newNode(Exp, yylineno, 3, children, nullValue());
+	}
+    	| Exp MINUS Exp {
+		pNode children[3] = { $1, $2, $3 };
+		$$ = newNode(Exp, yylineno, 3, children, nullValue());
+	}
+    	| Exp TIMES Exp {
+		pNode children[3] = { $1, $2, $3 };
+		$$ = newNode(Exp, yylineno, 3, children, nullValue());
+	}
+    	| Exp DIV Exp {
+		pNode children[3] = { $1, $2, $3 };
+		$$ = newNode(Exp, yylineno, 3, children, nullValue());
+	}
+    	| LP Exp RP {
+		pNode children[3] = { $1, $2, $3 };
+		$$ = newNode(Exp, yylineno, 3, children, nullValue());
+	}
+    	| MINUS Exp {
+		pNode children[2] = { $1, $2 };
+		$$ = newNode(Exp, yylineno, 2, children, nullValue());
+	}
+    	| NOT Exp {
+		pNode children[2] = { $1, $2 };
+		$$ = newNode(Exp, yylineno, 2, children, nullValue());
+	}
+    	| ID LP Args RP {
+		pNode children[4] = { $1, $2, $3, $4 };
+		$$ = newNode(Exp, yylineno, 4, children, nullValue());
+	}
+    	| ID LP RP {
+		pNode children[3] = { $1, $2, $3 };
+		$$ = newNode(Exp, yylineno, 3, children, nullValue());
+	}
+    	| Exp LB Exp RB {
+		pNode children[4] = { $1, $2, $3, $4 };
+		$$ = newNode(Exp, yylineno, 4, children, nullValue());
+	}
+    	| Exp DOT ID {
+		pNode children[3] = { $1, $2, $3 };
+		$$ = newNode(Exp, yylineno, 3, children, nullValue());
+	}
+    	| ID {
+		pNode children[1] = { $1 };
+		$$ = newNode(Exp, yylineno, 1, children, nullValue());
+	}
+    	| INTEGER {
+		pNode children[1] = { $1 };
+		$$ = newNode(Exp, yylineno, 1, children, nullValue());
+	}
+    	| FLOAT {
+		pNode children[1] = { $1 };
+		$$ = newNode(Exp, yylineno, 1, children, nullValue());
+	}
+    	;
+
+Args:
+   	Exp COMMA Args {
+		pNode children[3] = { $1, $2, $3 };
+		$$ = newNode(Args, yylineno, 3, children, nullValue());
+	}
+    	| Exp {
+		pNode children[1] = { $1 };
+		$$ = newNode(Exp, yylineno, 1, children, nullValue());
+	}
+    	;
+
+%%
+
+void yyerror(char const *s) {
+	errors += 1;
+	fprintf(stderr, "Error type B at Line %d: \"%s\".\n", yylineno, s);
+}
diff --git a/scanner.l b/scanner.l
new file mode 100644
index 0000000..b3291fc
--- /dev/null
+++ b/scanner.l
@@ -0,0 +1,188 @@
+%{
+	#include "parser.tab.h"
+	#include "node.h"
+	#include <stdio.h>
+	#include <stdlib.h>
+	extern int errors;
+%}
+
+%option yylineno
+
+DEC_DIGIT [0-9]
+HEX_DIGIT [0-9a-fA-F]
+OCT_DIGIT [0-8]
+DEC_INTEGER [+-]?(0|[1-9]{DEC_DIGIT}*)
+HEX_INTEGER [+-]?0[xX]{HEX_DIGIT}+
+OCT_INTEGER [+-]?0{OCT_DIGIT}+
+FLOAT [+-]?{DEC_DIGIT}*\.{DEC_DIGIT}+([eE][-+]?{DEC_DIGIT}+)?
+
+NEWLINE (\n|\r\n)
+WHITE_SPACE [ \t]
+SEMI ";"
+COMMA ","
+ASSIGNOP "="
+PLUS "+"
+MINUS "-"
+TIMES "*"
+DIV "/"
+AND "&&"
+OR "||"
+DOT "."
+NOT "!"
+LP "("
+RP ")"
+LB "["
+RB "]"
+LC "{"
+RC "}"
+STRUCT "struct"
+RETURN "return"
+IF "if"
+ELSE "else"
+WHILE "while"
+TYPE_INT "int"
+TYPE_FLOAT "float"
+ID [a-zA-Z_][a-zA-Z0-9_]*
+LINE_COMMENT \/\/.*$
+BLOCK_COMMENT \/\*(.|\n)*?\*\/
+
+%%
+{SEMI} {
+	yylval = newNode(Semi, yylineno, 0, NULL, nullValue());
+	return SEMI;
+}
+{COMMA} {
+	yylval = newNode(Comma, yylineno, 0, NULL, nullValue());
+	return COMMA;
+}
+{ASSIGNOP} {
+	yylval = newNode(Assignop, yylineno, 0, NULL, nullValue());
+	return ASSIGNOP;
+}
+{PLUS} {
+	yylval = newNode(Plus, yylineno, 0, NULL, nullValue());
+	return PLUS;
+}
+{MINUS} {
+	yylval = newNode(Minus, yylineno, 0, NULL, nullValue());
+	return MINUS;
+}
+{TIMES} {
+	yylval = newNode(Times, yylineno, 0, NULL, nullValue());
+	return TIMES;
+}
+{DIV} {
+	yylval = newNode(Div, yylineno, 0, NULL, nullValue());
+	return DIV;
+}
+{AND} {
+	yylval = newNode(And, yylineno, 0, NULL, nullValue());
+	return AND;
+}
+{OR} {
+	yylval = newNode(Or, yylineno, 0, NULL, nullValue());
+	return OR;
+}
+{DOT} {
+	yylval = newNode(Dot, yylineno, 0, NULL, nullValue());
+	return DOT;
+}
+{NOT} {
+	yylval = newNode(Not, yylineno, 0, NULL, nullValue());
+	return NOT;
+}
+{LP} {
+	yylval = newNode(Lp, yylineno, 0, NULL, nullValue());
+	return LP;
+}
+{RP} {
+	yylval = newNode(Rp, yylineno, 0, NULL, nullValue());
+	return RP;
+}
+{LB} {
+	yylval = newNode(Lb, yylineno, 0, NULL, nullValue());
+	return LB;
+}
+{RB} {
+	yylval = newNode(Rb, yylineno, 0, NULL, nullValue());
+	return RB;
+}
+{LC} {
+	yylval = newNode(Lc, yylineno, 0, NULL, nullValue());
+	return LC;
+}
+{RC} {
+	yylval = newNode(Rc, yylineno, 0, NULL, nullValue());
+	return RC;
+}
+{STRUCT} {
+	yylval = newNode(Struct, yylineno, 0, NULL, nullValue());
+	return STRUCT;
+}
+{RETURN} {
+	yylval = newNode(Return, yylineno, 0, NULL, nullValue());
+	return RETURN;
+}
+{IF} {
+	yylval = newNode(If, yylineno, 0, NULL, nullValue());
+	return IF;
+}
+{ELSE} {
+	yylval = newNode(Else, yylineno, 0, NULL, nullValue());
+	return ELSE;
+}
+{WHILE} {
+	yylval = newNode(While, yylineno, 0, NULL, nullValue());
+	return WHILE;
+}
+{TYPE_INT} {
+	yylval = newNode(Type_int, yylineno, 0, NULL, nullValue());
+	return TYPE_INT;
+}
+{TYPE_FLOAT} {
+	yylval = newNode(Type_float, yylineno, 0, NULL, nullValue());
+	return TYPE_FLOAT;
+}
+{DEC_INTEGER} {
+	ValueUnion value = { .integer = strtol(yytext, NULL, 10) };
+	yylval = newNode(Integer, yylineno, 0, NULL, value);
+	return INTEGER; 
+}
+{HEX_INTEGER} {
+	ValueUnion value = { .integer = strtol(yytext, NULL, 16) };
+	yylval = newNode(Integer, yylineno, 0, NULL, value);
+	return INTEGER; 
+}
+{OCT_INTEGER} {
+	ValueUnion value = { .integer = strtol(yytext, NULL, 8) };
+	yylval = newNode(Integer, yylineno, 0, NULL, value);
+	return INTEGER; 
+}
+{FLOAT} {
+	ValueUnion value = { .real = atof(yytext) };
+	yylval = newNode(Float, yylineno, 0, NULL, value);
+	return FLOAT;
+}
+{ID} {
+	char* id = (char*)calloc(sizeof(char), yyleng + 1);
+	strcpy(id, yytext);
+	ValueUnion value = { .id = id };
+	yylval = newNode(Ident, yylineno, 0, NULL, value);
+	return ID;
+}
+{LINE_COMMENT} {
+	yylval = newNode(Line_comment, yylineno, 0, NULL, nullValue());
+	return LINE_COMMENT;
+}
+{BLOCK_COMMENT} {
+	yylval = newNode(Block_comment, yylineno, 0, NULL, nullValue());
+	return BLOCK_COMMENT;
+}
+{NEWLINE}|{WHITE_SPACE} {}
+. {
+	errors += 1;
+	fprintf(stderr, "Error type A at Line %d: Mysterious character \"%s\".\n", yylineno, yytext);
+	return YYerror;
+}
+%%
+