diff --git a/src/ASTPrinter.cpp b/src/ASTPrinter.cpp
deleted file mode 100644
index 47e9f92..0000000
--- a/src/ASTPrinter.cpp
+++ /dev/null
@@ -1,28 +0,0 @@
-#include <algorithm>
-#include <iostream>
-using namespace std;
-#include "ASTPrinter.h"
-#include "SysYParser.h"
-
-any ASTPrinter::visitNumber(SysYParser::NumberContext *ctx) {
-  cout << ctx->IntConst()->getText();
-  return nullptr;
-}
-
-any ASTPrinter::visitString(SysYParser::StringContext *ctx) {
-  cout << ctx->String()->getText();
-  return nullptr;
-}
-
-any ASTPrinter::visitFuncRParams(SysYParser::FuncRParamsContext *ctx) {
-  if (ctx->funcRParam().empty())
-    return nullptr;
-  auto numParams = ctx->funcRParam().size();
-  ctx->funcRParam(0)->accept(this);
-  for (int i = 1; i < numParams; ++i) {
-    cout << ", ";
-    ctx->funcRParam(i)->accept(this);
-  }
-  cout << '\n';
-  return nullptr;
-}
diff --git a/src/ASTPrinter.h b/src/ASTPrinter.h
index ed68869..1294c46 100644
--- a/src/ASTPrinter.h
+++ b/src/ASTPrinter.h
@@ -1,12 +1,181 @@
 #pragma once
 
-#include "SysYBaseVisitor.h"
+#include "SysYBaseListener.h"
+#include <ostream>
+
+class SysYASTPrinter : public SysYBaseListener {
+  std::ostream &os;
+  int indent;
 
-class ASTPrinter : public SysYBaseVisitor {
 public:
-  std::any visitFuncRParams(SysYParser::FuncRParamsContext *ctx) override;
-//   std::any visitExpAsRParam(SysYParser::ExpAsRParamContext *ctx) override;
-//   std::any visitStringAsRParam(SysYParser::StringAsRParamContext *ctx) override;
-  std::any visitNumber(SysYParser::NumberContext *ctx) override;
-  std::any visitString(SysYParser::StringContext *ctx) override;
-};
\ No newline at end of file
+  SysYASTPrinter(std::ostream &os = std::cout) : os(os), indent(0) {}
+
+protected:
+  void enter(const std::string &name) {
+    os << std::string(indent, ' ') << name << '\n';
+    indent += 2;
+  }
+  void exit() { indent -= 2; }
+
+public:
+  virtual void enterModule(SysYParser::ModuleContext * /*ctx*/) override {
+    enter("module");
+  }
+
+  virtual void enterDecl(SysYParser::DeclContext * /*ctx*/) override {
+    enter("decl");
+  }
+
+  virtual void enterBtype(SysYParser::BtypeContext * /*ctx*/) override {
+    enter("btype");
+  }
+
+  // virtual void
+  // enterConstValue(SysYParser::ConstValueContext * /*ctx*/) override {
+  //   enter("constValue");
+  // }
+
+  virtual void enterVarDef(SysYParser::VarDefContext *ctx) override {
+    enter("varDef");
+  }
+
+  virtual void enterFunc(SysYParser::FuncContext * /*ctx*/) override {
+    enter("func");
+  }
+
+  virtual void enterFuncType(SysYParser::FuncTypeContext * /*ctx*/) override {
+    enter("funcType");
+  }
+
+  virtual void
+  enterFuncFParams(SysYParser::FuncFParamsContext * /*ctx*/) override {
+    enter("funcFParams");
+  }
+
+  virtual void
+  enterFuncFParam(SysYParser::FuncFParamContext * /*ctx*/) override {
+    enter("funcFParam");
+  }
+
+  virtual void enterBlockStmt(SysYParser::BlockStmtContext * /*ctx*/) override {
+    enter("blockStmt");
+  }
+
+  virtual void enterBlockItem(SysYParser::BlockItemContext * /*ctx*/) override {
+    enter("blockIterm");
+  }
+
+  virtual void enterStmt(SysYParser::StmtContext * /*ctx*/) override {
+    enter("stmt");
+  }
+
+  virtual void
+  enterAssignStmt(SysYParser::AssignStmtContext * /*ctx*/) override {
+    enter("assignStmt");
+  }
+
+  virtual void enterExpStmt(SysYParser::ExpStmtContext * /*ctx*/) override {
+    enter("expStmt");
+  }
+
+  virtual void enterIfStmt(SysYParser::IfStmtContext *ctx) override {
+    enter("ifStmt " + ctx->getText());
+  }
+
+  virtual void enterWhileStmt(SysYParser::WhileStmtContext * /*ctx*/) override {
+    enter("whileStmt");
+  }
+
+  virtual void enterBreakStmt(SysYParser::BreakStmtContext * /*ctx*/) override {
+    enter("break");
+  }
+
+  virtual void
+  enterContinueStmt(SysYParser::ContinueStmtContext * /*ctx*/) override {
+    enter("continueStmt");
+  }
+
+  virtual void
+  enterReturnStmt(SysYParser::ReturnStmtContext * /*ctx*/) override {
+    enter("returnStmt");
+  }
+
+  virtual void enterEmptyStmt(SysYParser::EmptyStmtContext * /*ctx*/) override {
+    enter("emptyStmt");
+  }
+
+  virtual void enterRelationExp(SysYParser::RelationExpContext *ctx) override {
+    enter(std::string("relationExp: ") + ctx->getText());
+  }
+
+  virtual void
+  enterMultiplicativeExp(SysYParser::MultiplicativeExpContext *ctx) override {
+    enter(std::string("multiplicativeExp: ") + ctx->getText());
+  }
+
+  virtual void enterCallExp(SysYParser::CallExpContext * ctx) override {
+    enter("callExp " + ctx->getText());
+  }
+  virtual void enterLValueExp(SysYParser::LValueExpContext * /*ctx*/) override {
+    enter("lValueExp");
+  }
+
+  virtual void enterNumberExp(SysYParser::NumberExpContext * /*ctx*/) override {
+    enter("numberExp");
+  }
+
+  virtual void enterAndExp(SysYParser::AndExpContext * /*ctx*/) override {
+    enter("andExp");
+  }
+
+  virtual void enterUnaryExp(SysYParser::UnaryExpContext *ctx) override {
+    enter(std::string("multiplicativeExp: ") + ctx->getText());
+  }
+
+  virtual void enterParenExp(SysYParser::ParenExpContext * /*ctx*/) override {
+    enter("parenExp");
+  }
+
+  virtual void enterStringExp(SysYParser::StringExpContext * /*ctx*/) override {
+    enter("stringExp");
+  }
+
+  virtual void enterOrExp(SysYParser::OrExpContext * /*ctx*/) override {
+    enter("orExp");
+  }
+
+  virtual void enterAdditiveExp(SysYParser::AdditiveExpContext *ctx) override {
+    enter(std::string("additiveExp: ") + ctx->getText());
+  }
+
+  virtual void enterEqualExp(SysYParser::EqualExpContext *ctx) override {
+    enter(std::string("equalExp: ") + ctx->getText());
+  }
+
+  virtual void enterLValue(SysYParser::LValueContext * /*ctx*/) override {
+    enter("lValue");
+  }
+
+  virtual void enterNumber(SysYParser::NumberContext * /*ctx*/) override {
+    enter("number");
+  }
+
+  virtual void enterString(SysYParser::StringContext * /*ctx*/) override {
+    enter("string");
+  }
+
+  virtual void
+  enterFuncRParams(SysYParser::FuncRParamsContext * /*ctx*/) override {
+    enter("funcRparams");
+  }
+
+  virtual void enterEveryRule(antlr4::ParserRuleContext *ctx) override {
+    // os << ctx->getText();
+    // enter("");
+  }
+  virtual void exitEveryRule(antlr4::ParserRuleContext * /*ctx*/) override {
+    exit();
+  }
+  virtual void visitTerminal(antlr4::tree::TerminalNode * /*node*/) override {}
+  virtual void visitErrorNode(antlr4::tree::ErrorNode * /*node*/) override {}
+};
diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 68f8942..d0bc1c6 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -5,6 +5,7 @@ antlr_target(SysYGen SysY.g4
   LEXER PARSER
   OUTPUT_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR}
   VISITOR
+  LISTENER
 )
 
 add_library(SysYParser SHARED ${ANTLR_SysYGen_CXX_OUTPUTS})
@@ -13,7 +14,7 @@ target_link_libraries(SysYParser PUBLIC antlr4_shared)
 
 add_executable(sysyc
   sysyc.cpp
-  ASTPrinter.cpp
+  SysYFormatter.cpp
 )
 target_include_directories(sysyc PRIVATE ${CMAKE_CURRENT_BINARY_DIR})
 target_link_libraries(sysyc PRIVATE SysYParser)
diff --git a/src/SysY.g4 b/src/SysY.g4
index 0f7790a..b6b4232 100644
--- a/src/SysY.g4
+++ b/src/SysY.g4
@@ -4,33 +4,165 @@ grammar SysY;
 /* Lexer rules                                     */
 /*===-------------------------------------------===*/
 
-Comma: ',';
+// fragments
 
-fragment Decimal: [0-9];
-fragment Octal: [0-7];
-fragment Heximal: [0-9a-fA-F];
-fragment NonZeroDecimal: [1-9];
+// keywords
+CONST: 'const';
+INT: 'int';
+FLOAT: 'float';
+VOID: 'void';
+IF: 'if';
+ELSE: 'else';
+WHILE: 'while';
+BREAK: 'break';
+CONTINUE: 'continue';
+RETURN: 'return';
 
-IntConst: NonZeroDecimal Decimal*
-        | '0' Octal+
-		| ('0x' | '0X') Heximal+;
+// operators
+ASSIGN: '=';
+ADD: '+';
+SUB: '-';
+MUL: '*';
+DIV: '/';
+MODULO: '%';
+LT: '<';
+GT: '>';
+LE: '<=';
+GE: '>=';
+EQ: '==';
+NE: '!=';
+AND: '&&';
+OR: '||';
+NOT: '!';
 
-String: '"' (ESC | .)*? '"';
+// punctuations
+LPAREN: '(';
+RPAREN: ')';
+LBRACKET: '[';
+RBRACKET: ']';
+LBRACE: '{';
+RBRACE: '}';
+COMMA: ',';
+SEMICOLON: ';';
 
+// identifier
+fragment ALPHA: [a-zA-Z];
+fragment ALPHANUM: [a-zA-Z0-9];
+fragment NONDIGIT: [a-zA-Z_];
+ID: NONDIGIT (ALPHANUM | '_')*;
+
+// literals
+fragment DecDigit: [0-9];
+fragment OctDigit: [0-7];
+fragment HexDigit: [0-9a-fA-F];
+fragment OctPrefix: '0';
+fragment HexPrefix: '0' [xX];
+fragment NonZeroDecDigit: [1-9];
+fragment Sign: [+-];
+fragment DecFractional: DecDigit* '.' DecDigit+ | DecDigit+ '.';
+fragment Exponent: [eE] Sign? DecDigit+;
+fragment DecFloat: DecFractional Exponent? | DecDigit+ Exponent;
+fragment HexFractional: HexDigit* '.' HexDigit+ | HexDigit+ '.';
+fragment BinExponent: [pP] Sign? DecDigit+;
+fragment HexFloat:
+	HexPrefix HexFractional BinExponent
+	| HexDigit+ BinExponent;
+
+ILITERAL:
+	NonZeroDecDigit DecDigit*
+	| OctPrefix OctDigit*
+	| HexPrefix HexDigit+;
+
+FLITERAL: DecFloat | HexFloat;
+
+// string
 fragment ESC: '\\"' | '\\\\';
+STRING: '"' (ESC | .)*? '"';
 
+// white space and comments
 WS: [ \t\r\n] -> skip;
-
-LINE_COMMENT: '//' .*? '\r'? '\n' -> skip;
-COMMENT: '/*' .*? '*/' -> skip;
+LINECOMMENT: '//' .*? '\r'? '\n' -> skip;
+BLOCKCOMMENT: '/*' .*? '*/' -> skip;
 
 /*===-------------------------------------------===*/
 /* Syntax rules                                    */
 /*===-------------------------------------------===*/
 
-funcRParams: funcRParam (Comma funcRParam)* EOF;
+module: (decl | func)+;
+
+// constDecl and varDecl shares the same syntax structure, except that constDecl must have constant
+// initial values. We combine these two syntax rules, and ensure the constraint above at the
+// semantic check phase.
+decl: CONST? btype varDef (COMMA varDef)* SEMICOLON;
+
+btype: INT | FLOAT;
+
+varDef: lValue (ASSIGN initValue)?;
+
+initValue:
+	exp											# scalarInitValue
+	| LBRACE (initValue (COMMA initValue)*)?	# arrayInitValue;
+
+func: funcType ID LPAREN funcFParams? RPAREN blockStmt;
+
+funcType: VOID | INT | FLOAT;
+
+funcFParams: funcFParam (COMMA funcFParam)*;
+
+funcFParam:
+	btype ID (LBRACKET RBRACKET (LBRACKET exp RBRACKET)*)?;
+
+blockStmt: LBRACE blockItem* RBRACE;
+
+blockItem: decl | stmt;
+
+stmt:
+	assignStmt
+	| expStmt
+	| ifStmt
+	| whileStmt
+	| breakStmt
+	| continueStmt
+	| returnStmt
+	| blockStmt
+	| emptyStmt;
+
+assignStmt: lValue ASSIGN exp SEMICOLON;
+
+expStmt: exp SEMICOLON;
+
+ifStmt: IF LPAREN exp RPAREN stmt (ELSE stmt)?;
+
+whileStmt: WHILE LPAREN exp RPAREN stmt;
+
+breakStmt: BREAK SEMICOLON;
+
+continueStmt: CONTINUE SEMICOLON;
+
+returnStmt: RETURN exp? SEMICOLON;
+
+emptyStmt: SEMICOLON;
+
+exp:
+	LPAREN exp RPAREN				# parenExp
+	| lValue						# lValueExp
+	| number						# numberExp
+	| string						# stringExp
+	| call							# callExp
+	| (ADD | SUB | NOT) exp			# unaryExp
+	| exp (MUL | DIV | MODULO) exp	# multiplicativeExp
+	| exp (ADD | SUB) exp			# additiveExp
+	| exp (LT | GT | LE | GE) exp	# relationExp
+	| exp (EQ | NE) exp				# equalExp
+	| exp AND exp					# andExp
+	| exp OR exp					# orExp;
+
+call: ID LPAREN funcRParams? RPAREN;
+
+lValue: ID (LBRACKET exp RBRACKET)*;
+
+number: ILITERAL | FLITERAL;
 
-funcRParam: number # expAsRParam | string # stringAsRParam;
+string: STRING;
 
-number: IntConst;
-string: String;
+funcRParams: exp (COMMA exp)*;
diff --git a/src/SysYFormatter.cpp b/src/SysYFormatter.cpp
new file mode 100644
index 0000000..145b4e8
--- /dev/null
+++ b/src/SysYFormatter.cpp
@@ -0,0 +1,28 @@
+#include <algorithm>
+#include <iostream>
+using namespace std;
+#include "SysYParser.h"
+#include "SysYFormatter.h"
+
+// any ASTPrinter::visitNumber(SysYParser::NumberContext *ctx) {
+//   cout << ctx->IntConst()->getText();
+//   return nullptr;
+// }
+
+// any ASTPrinter::visitString(SysYParser::StringContext *ctx) {
+//   cout << ctx->String()->getText();
+//   return nullptr;
+// }
+
+// any ASTPrinter::visitFuncRParams(SysYParser::FuncRParamsContext *ctx) {
+//   if (ctx->funcRParam().empty())
+//     return nullptr;
+//   auto numParams = ctx->funcRParam().size();
+//   ctx->funcRParam(0)->accept(this);
+//   for (int i = 1; i < numParams; ++i) {
+//     cout << ", ";
+//     ctx->funcRParam(i)->accept(this);
+//   }
+//   cout << '\n';
+//   return nullptr;
+// }
diff --git a/src/SysYFormatter.h b/src/SysYFormatter.h
new file mode 100644
index 0000000..ac6192b
--- /dev/null
+++ b/src/SysYFormatter.h
@@ -0,0 +1,334 @@
+#pragma once
+
+#include "SysYBaseVisitor.h"
+#include "SysYParser.h"
+#include <ostream>
+
+class SysYFormatter : public SysYBaseVisitor {
+protected:
+  std::ostream &os;
+  int indent = 0;
+
+public:
+  SysYFormatter(std::ostream &os) : os(os), indent(0) {}
+
+protected:
+  struct Indentor {
+    static constexpr int TabSize = 2;
+    int &indent;
+    Indentor(int &indent) : indent(indent) { indent += TabSize; }
+    ~Indentor() { indent -= TabSize; }
+  };
+  std::ostream &space() { return os << std::string(indent, ' '); }
+  template <typename T>
+  std::ostream &interleave(const T &container, const std::string sep = ", ") {
+    auto b = container.begin(), e = container.end();
+    (*b)->accept(this);
+    for (b = std::next(b); b != e; b = std::next(b)) {
+      os << sep;
+      (*b)->accept(this);
+    }
+    return os;
+  }
+
+public:
+//   virtual std::any visitModule(SysYParser::ModuleContext *ctx) override {
+//     return visitChildren(ctx);
+//   }
+
+  virtual std::any visitBtype(SysYParser::BtypeContext *ctx) override {
+    os << ctx->getText();
+    return 0;
+  }
+
+  virtual std::any visitDecl(SysYParser::DeclContext *ctx) override {
+    space();
+    if (ctx->CONST())
+      os << ctx->CONST()->getText() << ' ';
+    ctx->btype()->accept(this);
+    os << ' ';
+    interleave(ctx->varDef(), ", ") << ';' << '\n';
+    return 0;
+  }
+
+  virtual std::any visitVarDef(SysYParser::VarDefContext *ctx) override {
+    ctx->lValue()->accept(this);
+    if (ctx->initValue()) {
+      os << ' ' << '=' << ' ';
+      ctx->initValue()->accept(this);
+    }
+    return 0;
+  }
+
+  virtual std::any
+  visitArrayInitValue(SysYParser::ArrayInitValueContext *ctx) override {
+    os << '{';
+    auto values = ctx->initValue();
+    if (values.size())
+      interleave(values, ", ");
+    os << '}';
+    return 0;
+  }
+
+  virtual std::any visitFunc(SysYParser::FuncContext *ctx) override {
+    ctx->funcType()->accept(this);
+    os << ' ' << ctx->ID()->getText() << '(';
+    if (ctx->funcFParams())
+      ctx->funcFParams()->accept(this);
+    os << ')' << ' ';
+    ctx->blockStmt()->accept(this);
+    os << '\n';
+    return 0;
+  }
+
+  virtual std::any visitFuncType(SysYParser::FuncTypeContext *ctx) override {
+    os << ctx->getText();
+    return 0;
+  }
+
+  virtual std::any
+  visitFuncFParams(SysYParser::FuncFParamsContext *ctx) override {
+    interleave(ctx->funcFParam(), ", ");
+    return 0;
+  }
+
+  virtual std::any
+  visitFuncFParam(SysYParser::FuncFParamContext *ctx) override {
+    ctx->btype()->accept(this);
+    os << ' ' << ctx->ID()->getText();
+    if (not ctx->LBRACKET().empty()) {
+      os << '[';
+      auto exp = ctx->exp();
+      if (not exp.empty()) {
+        os << '[';
+        interleave(exp, "][") << ']';
+      }
+    }
+    return 0;
+  }
+
+  virtual std::any visitBlockStmt(SysYParser::BlockStmtContext *ctx) override {
+    os << '{' << '\n';
+    {
+      Indentor indentor(indent);
+      auto items = ctx->blockItem();
+      if (not items.empty())
+        interleave(items, "");
+    }
+    space() << ctx->RBRACE()->getText() << '\n';
+    return 0;
+  }
+
+  //   virtual std::any visitBlockItem(SysYParser::BlockItemContext *ctx)
+  //   override {
+  //     return visitChildren(ctx);
+  //   }
+
+  //   virtual std::any visitStmt(SysYParser::StmtContext *ctx) override {
+  //     return visitChildren(ctx);
+  //   }
+
+  virtual std::any
+  visitAssignStmt(SysYParser::AssignStmtContext *ctx) override {
+    space();
+    ctx->lValue()->accept(this);
+    os << " = ";
+    ctx->exp()->accept(this);
+    os << ';' << '\n';
+    return 0;
+  }
+
+  virtual std::any visitExpStmt(SysYParser::ExpStmtContext *ctx) override {
+    space();
+    ctx->exp()->accept(this);
+    os << ';' << '\n';
+    return 0;
+  }
+
+  void wrapBlock(SysYParser::StmtContext *stmt) {
+    bool isBlock = stmt->blockStmt();
+    if (isBlock) {
+      stmt->accept(this);
+    } else {
+      os << "{\n";
+      {
+        Indentor indentor(indent);
+        stmt->accept(this);
+      }
+      space() << "}\n";
+    }
+  };
+  virtual std::any visitIfStmt(SysYParser::IfStmtContext *ctx) override {
+    space();
+    os << ctx->IF()->getText() << " (";
+    ctx->exp()->accept(this);
+    os << ") ";
+    auto stmt = ctx->stmt();
+    auto ifStmt = stmt[0];
+    wrapBlock(ifStmt);
+    if (stmt.size() == 2) {
+      auto elseStmt = stmt[1];
+      wrapBlock(elseStmt);
+    }
+    return 0;
+  }
+
+  virtual std::any visitWhileStmt(SysYParser::WhileStmtContext *ctx) override {
+    space();
+    os << ctx->WHILE()->getText() << " (";
+    ctx->exp()->accept(this);
+    os << ") ";
+    wrapBlock(ctx->stmt());
+    return 0;
+  }
+
+  virtual std::any visitBreakStmt(SysYParser::BreakStmtContext *ctx) override {
+    space() << ctx->BREAK()->getText() << ';' << '\n';
+    return 0;
+  }
+
+  virtual std::any
+  visitContinueStmt(SysYParser::ContinueStmtContext *ctx) override {
+    space() << ctx->CONTINUE()->getText() << ';'
+            << '\n';
+    return 0;
+  }
+
+  virtual std::any
+  visitReturnStmt(SysYParser::ReturnStmtContext *ctx) override {
+    space() << ctx->RETURN()->getText();
+    if (ctx->exp()) {
+      os << ' ';
+      ctx->exp()->accept(this);
+    }
+    os << ';' << '\n';
+    return 0;
+  }
+
+  //   virtual std::any visitEmptyStmt(SysYParser::EmptyStmtContext *ctx)
+  //   override {
+  //     return visitChildren(ctx);
+  //   }
+
+  virtual std::any
+  visitRelationExp(SysYParser::RelationExpContext *ctx) override {
+    auto lhs = ctx->exp(0);
+    auto rhs = ctx->exp(1);
+    std::string op =
+        ctx->LT() ? "<" : (ctx->LE() ? "<=" : (ctx->GT() ? ">" : ">="));
+    lhs->accept(this);
+    os << ' ' << op << ' ';
+    rhs->accept(this);
+    return 0;
+  }
+
+  virtual std::any
+  visitMultiplicativeExp(SysYParser::MultiplicativeExpContext *ctx) override {
+    auto lhs = ctx->exp(0);
+    auto rhs = ctx->exp(1);
+    std::string op = ctx->MUL() ? "*" : (ctx->DIV() ? "/" : "%");
+    lhs->accept(this);
+    os << ' ' << op << ' ';
+    rhs->accept(this);
+    return 0;
+  }
+
+//   virtual std::any visitLValueExp(SysYParser::LValueExpContext *ctx) override {
+//     return visitChildren(ctx);
+//   }
+
+//   virtual std::any visitNumberExp(SysYParser::NumberExpContext *ctx) override {
+//     return visitChildren(ctx);
+//   }
+
+  virtual std::any visitAndExp(SysYParser::AndExpContext *ctx) override {
+    ctx->exp(0)->accept(this);
+    os << " && ";
+    ctx->exp(1)->accept(this);
+    return 0;
+  }
+
+  virtual std::any visitUnaryExp(SysYParser::UnaryExpContext *ctx) override {
+    std::string op = ctx->ADD() ? "+" : (ctx->SUB() ? "-" : "!");
+    os << op;
+    ctx->exp()->accept(this);
+    return 0;
+  }
+
+  virtual std::any visitParenExp(SysYParser::ParenExpContext *ctx) override {
+    os << '(';
+    ctx->exp()->accept(this);
+    os << ')';
+    return 0;
+  }
+
+  virtual std::any visitStringExp(SysYParser::StringExpContext *ctx) override {
+    return visitChildren(ctx);
+  }
+
+  virtual std::any visitOrExp(SysYParser::OrExpContext *ctx) override {
+    ctx->exp(0)->accept(this);
+    os << " || ";
+    ctx->exp(1)->accept(this);
+    return 0;
+  }
+
+//   virtual std::any visitCallExp(SysYParser::CallExpContext *ctx) override {
+//     return visitChildren(ctx);
+//   }
+
+  virtual std::any
+  visitAdditiveExp(SysYParser::AdditiveExpContext *ctx) override {
+    auto lhs = ctx->exp(0);
+    auto rhs = ctx->exp(1);
+    std::string op = ctx->ADD() ? "+" : "-";
+    lhs->accept(this);
+    os << ' ' << op << ' ';
+    rhs->accept(this);
+    return 0;
+  }
+
+  virtual std::any visitEqualExp(SysYParser::EqualExpContext *ctx) override {
+    auto lhs = ctx->exp(0);
+    auto rhs = ctx->exp(1);
+    std::string op = ctx->EQ() ? "==" : "!=";
+    lhs->accept(this);
+    os << ' ' << op << ' ';
+    rhs->accept(this);
+    return 0;
+  }
+
+  virtual std::any visitCall(SysYParser::CallContext *ctx) override {
+    os << ctx->ID()->getText() << '(';
+    if (ctx->funcRParams())
+      ctx->funcRParams()->accept(this);
+    os << ')';
+    return 0;
+  }
+
+  virtual std::any visitLValue(SysYParser::LValueContext *ctx) override {
+    os << ctx->ID()->getText();
+    auto exp = ctx->exp();
+    if (not exp.empty()) {
+      os << '[';
+      interleave(exp, "][") << ']';
+    }
+    return 0;
+  }
+
+  virtual std::any visitNumber(SysYParser::NumberContext *ctx) override {
+    os << ctx->getText();
+    return 0;
+  }
+
+  virtual std::any visitString(SysYParser::StringContext *ctx) override {
+    os << ctx->getText();
+    return 0;
+  }
+
+  virtual std::any
+  visitFuncRParams(SysYParser::FuncRParamsContext *ctx) override {
+    interleave(ctx->exp(), ", ");
+    return 0;
+  }
+};
\ No newline at end of file
diff --git a/src/sysyc.cpp b/src/sysyc.cpp
index 3835829..4c2d1f3 100644
--- a/src/sysyc.cpp
+++ b/src/sysyc.cpp
@@ -1,12 +1,13 @@
 #include "ASTPrinter.h"
+#include "tree/ParseTreeWalker.h"
 #include <cstdlib>
 #include <fstream>
 #include <iostream>
 using namespace std;
 using namespace antlr4;
+#include "SysYFormatter.h"
 #include "SysYLexer.h"
 #include "SysYParser.h"
-#include "ASTPrinter.h"
 
 int main(int argc, char **argv) {
   if (argc != 2) {
@@ -22,10 +23,13 @@ int main(int argc, char **argv) {
   SysYLexer lexer(&input);
   CommonTokenStream tokens(&lexer);
   SysYParser parser(&tokens);
-  SysYParser::FuncRParamsContext *params = parser.funcRParams();
-  
-  ASTPrinter printer;
-  printer.visitFuncRParams(params);
+  auto module = parser.module();
+  // tree::ParseTreeWalker walker;
+  // SysYASTPrinter printer(cout);
+  // cout << module->getText() << '\n';
+  // walker.walk(&printer, module);
+  SysYFormatter formatter(cout);
+  formatter.visitModule(module);
 
   return EXIT_SUCCESS;
 }
\ No newline at end of file