diff --git a/bootstrap/emit.cc b/bootstrap/emit.cc
index dcada32..dba673e 100644
--- a/bootstrap/emit.cc
+++ b/bootstrap/emit.cc
@@ -20,9 +20,9 @@ std::any EmitVisitor::visitFunction(xlangParser::FunctionContext *ctx) {
   output << std::endl
          << "export function w $" << ctx->Identifier()->getSymbol()->getText()
          << "(";
-  if (auto arg_list = ctx->argumentList()) {
-    for (const auto arg : arg_list->Identifier()) {
-      output << "w %_" << arg->getSymbol()->getText() << ", ";
+  if (auto param_list = ctx->parameterList()) {
+    for (const auto param : param_list->Identifier()) {
+      output << "w %_" << param->getSymbol()->getText() << ", ";
     }
   }
   output << ")" << std::endl << "{" << std::endl << "@start" << std::endl;
@@ -36,7 +36,7 @@ std::any EmitVisitor::visitFunction(xlangParser::FunctionContext *ctx) {
 std::any EmitVisitor::visitStatement(xlangParser::StatementContext *ctx) {
   if (auto identifier = ctx->Identifier()) {
     tmpcount = 0;
-    visitExpr(ctx->expr());
+    visitValue(ctx->value());
     output << "  %_" << identifier->getSymbol()->getText() << " = w copy "
            << last << std::endl;
     return {};
@@ -73,14 +73,14 @@ std::any EmitVisitor::visitStatement(xlangParser::StatementContext *ctx) {
   }
   if (ctx->Return()) {
     tmpcount = 0;
-    visitExpr(ctx->expr());
+    visitValue(ctx->value());
     output << "  ret " << last << std::endl;
     output << "@dead" << blockcount++ << std::endl;
     return {};
   }
   if (ctx->Print()) {
     tmpcount = 0;
-    visitExpr(ctx->expr());
+    visitValue(ctx->value());
     output << "  call $printf(l $printformat, ..., w " << last << ")"
            << std::endl;
     return {};
@@ -129,7 +129,7 @@ std::any EmitVisitor::visitBoolean(xlangParser::BooleanContext *ctx) {
     last = "0";
     return {};
   }
-  visitCondition(ctx->condition());
+  visitChildren(ctx);
   return {};
 }
 
@@ -169,27 +169,29 @@ std::any EmitVisitor::visitFactor(xlangParser::FactorContext *ctx) {
     last = integer->getSymbol()->getText();
     return {};
   }
-  if (auto identifier = ctx->Identifier()) {
-    if (ctx->LeftParen()) {
-      std::vector<std::string> args;
-      if (auto expr_list = ctx->exprList()) {
-        for (auto expr : expr_list->expr()) {
-          visitExpr(expr);
-          args.emplace_back(last);
-        }
+  visitChildren(ctx);
+  return {};
+}
+
+std::any EmitVisitor::visitVariable(xlangParser::VariableContext *ctx) {
+  auto name = ctx->Identifier()->getSymbol()->getText();
+
+  if (ctx->LeftParen()) {
+    std::vector<std::string> args;
+    if (auto arg_list = ctx->argumentList()) {
+      for (auto value : arg_list->value()) {
+        visitValue(value);
+        args.emplace_back(last);
       }
-      output << "  " << tmp() << " = w call $"
-             << identifier->getSymbol()->getText() << "(";
-      for (auto arg : args) {
-        output << "w " << arg << ", ";
-      }
-      output << ")" << std::endl;
-    } else {
-      last = "%_" + identifier->getSymbol()->getText();
     }
-    return {};
+    output << "  " << tmp() << " = w call $" << name << "(";
+    for (auto arg : args) {
+      output << "w " << arg << ", ";
+    }
+    output << ")" << std::endl;
+  } else {
+    last = "%_" + name;
   }
-  visitExpr(ctx->expr());
   return {};
 }
 
diff --git a/bootstrap/emit.hh b/bootstrap/emit.hh
index e86c9c0..889e4f8 100644
--- a/bootstrap/emit.hh
+++ b/bootstrap/emit.hh
@@ -26,6 +26,7 @@ class EmitVisitor : public xlangBaseVisitor {
   std::any visitExpr(xlangParser::ExprContext *ctx) override;
   std::any visitTerm(xlangParser::TermContext *ctx) override;
   std::any visitFactor(xlangParser::FactorContext *ctx) override;
+  std::any visitVariable(xlangParser::VariableContext *ctx) override;
 };
 
 }  // namespace xlang
diff --git a/bootstrap/typecheck.cc b/bootstrap/typecheck.cc
index f7b4cb3..274e305 100644
--- a/bootstrap/typecheck.cc
+++ b/bootstrap/typecheck.cc
@@ -26,8 +26,8 @@ std::any TypeCheckVisitor::visitFile(xlangParser::FileContext *ctx) {
                               "duplicate function '" + name + "'");
       continue;
     }
-    if (auto arg_list = function->argumentList()) {
-      function_arity[name] = arg_list->Identifier().size();
+    if (auto param_list = function->parameterList()) {
+      function_arity[name] = param_list->Identifier().size();
     } else {
       function_arity[name] = 0;
     }
@@ -38,9 +38,9 @@ std::any TypeCheckVisitor::visitFile(xlangParser::FileContext *ctx) {
 
 std::any TypeCheckVisitor::visitFunction(xlangParser::FunctionContext *ctx) {
   scope.emplace_back();
-  if (auto arg_list = ctx->argumentList()) {
-    for (const auto arg : arg_list->Identifier()) {
-      scope.back().emplace(arg->getSymbol()->getText());
+  if (auto param_list = ctx->parameterList()) {
+    for (const auto param : param_list->Identifier()) {
+      scope.back().emplace(param->getSymbol()->getText());
     }
   }
   visitBlock(ctx->block());
@@ -57,7 +57,7 @@ std::any TypeCheckVisitor::visitBlock(xlangParser::BlockContext *ctx) {
 
 std::any TypeCheckVisitor::visitStatement(xlangParser::StatementContext *ctx) {
   if (auto identifier = ctx->Identifier()) {
-    visitExpr(ctx->expr());
+    visitValue(ctx->value());
     scope.back().emplace(identifier->getSymbol()->getText());
     return {};
   }
@@ -65,45 +65,46 @@ std::any TypeCheckVisitor::visitStatement(xlangParser::StatementContext *ctx) {
   return {};
 }
 
-std::any TypeCheckVisitor::visitFactor(xlangParser::FactorContext *ctx) {
-  if (auto identifier = ctx->Identifier()) {
-    auto token = identifier->getSymbol();
-    auto name = token->getText();
-    if (ctx->LeftParen()) {
-      if (function_arity.find(name) != function_arity.end()) {
-        if (auto expr_list = ctx->exprList()) {
-          auto arity = function_arity[name];
-          auto arg_num = expr_list->expr().size();
-          if (arity != arg_num) {
-            errorlistener.typeError(
-                token->getLine(), token->getCharPositionInLine(),
-                "function '" + name + "' expects " + std::to_string(arity) +
-                    " arguments, but got " + std::to_string(arg_num));
-          }
-        } else {
-          if (auto arity = function_arity[name]) {
-            errorlistener.typeError(
-                token->getLine(), token->getCharPositionInLine(),
-                "function '" + name + "' expects " + std::to_string(arity) +
-                    " arguments, but got none");
-          }
+std::any TypeCheckVisitor::visitVariable(xlangParser::VariableContext *ctx) {
+  auto token = ctx->Identifier()->getSymbol();
+  auto name = token->getText();
+  auto line = token->getLine();
+  auto charPositionInLine = token->getCharPositionInLine();
+
+  if (ctx->LeftParen()) {
+    auto it = function_arity.find(name);
+
+    if (it == function_arity.end()) {
+      errorlistener.typeError(line, charPositionInLine,
+                              "unknown function '" + name + "'");
+    } else {
+      auto arity = it->second;
+
+      if (auto arg_list = ctx->argumentList()) {
+        auto arg_num = arg_list->value().size();
+
+        if (arity != arg_num) {
+          errorlistener.typeError(
+              line, charPositionInLine,
+              "function '" + name + "' expects " + std::to_string(arity) +
+                  " arguments, but got " + std::to_string(arg_num));
         }
       } else {
-        errorlistener.typeError(token->getLine(),
-                                token->getCharPositionInLine(),
-                                "unknown function '" + name + "'");
-      }
-      visitChildren(ctx);
-    } else {
-      if (!inScope(name)) {
-        errorlistener.typeError(token->getLine(),
-                                token->getCharPositionInLine(),
-                                "variable '" + name + "' is not in scope");
+        if (arity) {
+          errorlistener.typeError(line, charPositionInLine,
+                                  "function '" + name + "' expects " +
+                                      std::to_string(arity) +
+                                      " arguments, but got none");
+        }
       }
     }
-    return {};
+    visitChildren(ctx);
+  } else {
+    if (!inScope(name)) {
+      errorlistener.typeError(line, charPositionInLine,
+                              "variable '" + name + "' is not in scope");
+    }
   }
-  visitChildren(ctx);
   return {};
 }
 
diff --git a/bootstrap/typecheck.hh b/bootstrap/typecheck.hh
index b60290f..cf84daf 100644
--- a/bootstrap/typecheck.hh
+++ b/bootstrap/typecheck.hh
@@ -23,7 +23,7 @@ class TypeCheckVisitor : public xlangBaseVisitor {
   std::any visitFunction(xlangParser::FunctionContext *ctx) override;
   std::any visitBlock(xlangParser::BlockContext *ctx) override;
   std::any visitStatement(xlangParser::StatementContext *ctx) override;
-  std::any visitFactor(xlangParser::FactorContext *ctx) override;
+  std::any visitVariable(xlangParser::VariableContext *ctx) override;
 };
 
 }  // namespace xlang
diff --git a/bootstrap/xlang.g4 b/bootstrap/xlang.g4
index 6b23f6c..d2b7513 100644
--- a/bootstrap/xlang.g4
+++ b/bootstrap/xlang.g4
@@ -1,15 +1,18 @@
 grammar xlang;
 
 file  : function+ EOF;
-function  : Identifier LeftParen argumentList? RightParen block;
-argumentList  : Identifier (Comma Identifier)*;
+function  : Identifier LeftParen parameterList? RightParen block;
+parameterList  : Identifier (Comma Identifier)*;
 block : LeftBrace statement* RightBrace;
-statement : Identifier Assign expr Semicolon
+statement : Identifier Assign value Semicolon
           | If condition block (Else block)?
           | While condition block
-          | Return expr Semicolon
-          | Print expr Semicolon
+          | Return value Semicolon
+          | Print value Semicolon
           ;
+value : expr
+      | condition
+      ;
 condition : condition (And|Or|Xor) boolean
           | boolean
           ;
@@ -17,6 +20,7 @@ boolean : Not boolean
         | expr (Less|LessEqual|Greater|GreaterEqual|Equal|NotEqual) expr
         | True
         | False
+        | variable
         | LeftParen condition RightParen
         ;
 expr  : expr (Plus|Minus|BitAnd|BitOr|BitXor|ShiftLeft|ShiftRight) term
@@ -28,11 +32,13 @@ term  : term (Mul|Div) factor
 factor  : Minus factor
         | BitNot factor
         | Integer
-        | Identifier
-        | Identifier LeftParen exprList? RightParen
+        | variable
         | LeftParen expr RightParen
         ;
-exprList  : expr (Comma expr)*;
+variable  : Identifier
+          | Identifier LeftParen argumentList? RightParen
+          ;
+argumentList  : value (Comma value)*;
 
 If  : 'if';
 Else  : 'else';