@@ -101,12 +101,12 @@
 			auto e = tryEat("(")
 				? parseLambdaAfterOpenParen(pos)  // let var ( ...
 				: (eat("=", "after "~kwd), E(0)); // let var = ...
 			if( moreDeclarationExists() )
-				return new LetExpression(pos, var, SystemLayer, e, Body());
+				return new Let(pos, var, SystemLayer, e, Body());
 			else
-				return new LetExpression(pos, var, SystemLayer, e,
-					new LayExpression(pos, SystemLayer, new VarExpression(pos, var))
+				return new Let(pos, var, SystemLayer, e,
+					new Lay(pos, SystemLayer, new Var(pos, var))
 				);
 		}
 		else
 		{
@@ -120,11 +120,11 @@
 			auto e = tryEat("(")
 				? parseLambdaAfterOpenParen(varpos)  // let var ( ...
 				: (eat("=", "after "~kwd), E(0));    // let var = ...
 			if( moreDeclarationExists() )
-				return new LetExpression(pos, var, layer, e, Body());
+				return new Let(pos, var, layer, e, Body());
 			else
-				return new LetExpression(pos, var, layer, e, new VarExpression(varpos, var));
+				return new Let(pos, var, layer, e, new Var(varpos, var));
 		}
 	}
 
 	AST TopLevelExpression()
@@ -133,9 +133,9 @@
 
 		auto pos = currentPosition();
 		auto e = E(0);
 		if( moreDeclarationExists() )
-			return new LetExpression(pos, "_", "", e, Body());
+			return new Let(pos, "_", "", e, Body());
 		else
 			return e;
 	}
 
@@ -180,12 +180,12 @@
 			foreach(op; operator_perferences[level])
 				if( tryEat(op) )
 					if( op[0]=='.' )
 						return rec(
-							new FuncallExpression(lhs.pos, new VarExpression(pos, op), lhs, parseId()));
+							new App(lhs.pos, new Var(pos, op), lhs, parseId()));
 					else
-					return rec(
-						new FuncallExpression(lhs.pos, new VarExpression(pos, op), lhs, E(level+1)));
+						return rec(
+							new App(lhs.pos, new Var(pos, op), lhs, E(level+1)));
 			return lhs;
 		}
 
 		if( operator_perferences.length <= level )
@@ -212,9 +212,9 @@
 						eat(")", "after function parameters");
 						break;
 					}
 				}
-				e = new FuncallExpression(e.pos, e, args);
+				e = new App(e.pos, e, args);
 			}
 			else if( tryEat("{") )
 			{
 				e = parseTableSetAfterBrace(e);
@@ -233,10 +233,10 @@
 		{
 			string key = eatId("for table key", AllowQuoted);
 			eat(":", "after table key");
 			AST val = E(0);
-			e = new FuncallExpression(pos, new VarExpression(pos,".="),
-					e, new StrLiteral(pos,key), val);
+			e = new App(pos, new Var(pos,".="),
+					e, new Str(pos,key), val);
 			if( !tryEat(",") )
 			{
 				eat("}", "for the end of table literal");
 				break;
@@ -253,22 +253,22 @@
 		auto pos = lex.front.pos;
 		if( lex.front.quoted )
 		{
 			scope(exit) lex.popFront;
-			return new StrLiteral(pos, lex.front.str);
+			return new Str(pos, lex.front.str);
 		}
 		if( isNumber(lex.front.str) )
 		{
 			scope(exit) lex.popFront;
-			return new IntLiteral(pos, BigInt(cast(string)lex.front.str));
+			return new Int(pos, BigInt(cast(string)lex.front.str));
 		}
 		if( tryEat("@") )
 		{
 			auto lay = "@"~eatId("for layer ID");
 			eat("(", "for layered execution");
 			auto e = Body();
 			eat(")", "after "~lay~"(...");
-			return new LayExpression(pos, lay, e);
+			return new Lay(pos, lay, e);
 		}
 		if( tryEat("(") )
 		{
 			auto e = Body();
@@ -276,9 +276,9 @@
 			return e;
 		}
 		if( tryEat("{") )
 		{
-			AST e = new FuncallExpression(pos, new VarExpression(pos,"{}"));
+			AST e = new App(pos, new Var(pos,"{}"));
 			return parseTableSetAfterBrace(e);
 		}
 		if( tryEat("if") )
 		{
@@ -295,13 +295,13 @@
 				eat("{", "after else");
 				el = Body();
 				eat("}", "after else body");
 			}
-			return new FuncallExpression(pos, 
-				new VarExpression(pos, "if"),
+			return new App(pos, 
+				new Var(pos, "if"),
 				cond,
-				new FunLiteral(thenPos, [], th),
-				new FunLiteral(elsePos, [], el)
+				new Fun(thenPos, [], th),
+				new Fun(elsePos, [], el)
 			);
 		}
 		if( tryEat("case") )
 		{
@@ -312,9 +312,9 @@
 			eat("(", "after fun");
 			return parseLambdaAfterOpenParen(pos);
 		}
 		scope(exit) lex.popFront;
-		return new VarExpression(pos, lex.front.str);
+		return new Var(pos, lex.front.str);
 	}
 
 	AST parsePatternMatch(LexPosition pos)
 	{
@@ -326,10 +326,10 @@
 		eat(")", "after case");
 		string pmVar = freshVarName();
 		string pmTryFirst = freshVarName();
 		AST   pmBody = parsePatternMatchCases(pmVar, pmTryFirst,
-			new FuncallExpression(pos, new VarExpression(pos, pmTryFirst)));
-		return new LetExpression(pos, pmVar, [], pmExpr, pmBody);
+			new App(pos, new Var(pos, pmTryFirst)));
+		return new Let(pos, pmVar, [], pmExpr, pmBody);
 	}
 
 	AST parsePatternMatchCases(string pmVar, string tryThisBranchVar, AST thenDoThis)
 	{
@@ -346,23 +346,23 @@
 			auto pr = parsePattern();
 			eat(")", "after when");
 			eat("{", "after pattern");
 			AST cBody = Body();
-			AST judgement = new FuncallExpression(pos, new VarExpression(pos, "if"),
-				ppTest(pmVar, pr), new FunLiteral(pos,[],ppBind(pmVar, pr, cBody)),
-				new VarExpression(pos, failBranchVar));
+			AST judgement = new App(pos, new Var(pos, "if"),
+				ppTest(pmVar, pr), new Fun(pos,[],ppBind(pmVar, pr, cBody)),
+				new Var(pos, failBranchVar));
 			eat("}", "after pattern clause");
 			return parsePatternMatchCases(pmVar, failBranchVar, 
-				new LetExpression(pos, tryThisBranchVar, [],
-					new FunLiteral(pos,[],judgement), thenDoThis)
+				new Let(pos, tryThisBranchVar, [],
+					new Fun(pos,[],judgement), thenDoThis)
 			);
 		}
 		else
 		{
 			auto pos = currentPosition();
-			AST doNothing = new FunLiteral(pos,[],
-				new StrLiteral(pos, sprintf!"(pattern match failure:%s)"(pos)));
-			return new LetExpression(currentPosition(), tryThisBranchVar, [], doNothing, thenDoThis);
+			AST doNothing = new Fun(pos,[],
+				new Str(pos, sprintf!"(pattern match failure:%s)"(pos)));
+			return new Let(currentPosition(), tryThisBranchVar, [], doNothing, thenDoThis);
 		}
 	}
 
 // hageshiku tenuki
@@ -371,29 +371,29 @@
 		string[] path;
 		mixin SimpleClass;
 		private AST access(string pmVar, string[] path) {
 			auto pos = currentPosition();
-			AST e = new VarExpression(pos, pmVar);
+			AST e = new Var(pos, pmVar);
 			foreach(p; path)
-				e = new FuncallExpression(pos, new VarExpression(pos, "."), e, new StrLiteral(pos, p));
+				e = new App(pos, new Var(pos, "."), e, new Str(pos, p));
 			return e;
 		}
 		private AST has(AST e, string k) {
 			auto pos = currentPosition();
 			return opAndAnd(
-				new FuncallExpression(pos, new VarExpression(pos, "_istable"), e),
-				new FuncallExpression(pos, new VarExpression(pos, ".?"), e, new StrLiteral(pos, k))
+				new App(pos, new Var(pos, "_istable"), e),
+				new App(pos, new Var(pos, ".?"), e, new Str(pos, k))
 			);
 		}
 		private AST opAndAnd(AST a, AST b) {
 			if( a is null ) return b;
 			if( b is null ) return a;
 			auto pos = currentPosition();
-			return new FuncallExpression(pos,
-				new VarExpression(pos, "if"),
+			return new App(pos,
+				new Var(pos, "if"),
 				a,
-				new FunLiteral(pos, [], b),
-				new FunLiteral(pos, [], new IntLiteral(pos, 0))
+				new Fun(pos, [], b),
+				new Fun(pos, [], new Int(pos, 0))
 			);
 		}
 		AST ppTest(string pmVar) {
 			AST c = null;
@@ -412,9 +412,9 @@
 		string name;
 		mixin SimpleClass;
 		AST ppBind(string pmVar, AST thenDoThis) {
 			auto pos = currentPosition();
-			return new LetExpression(pos, name, [], access(pmVar,path), thenDoThis);
+			return new Let(pos, name, [], access(pmVar,path), thenDoThis);
 		}
 	}
 	class ConstantPattern : SinglePattern
 	{
@@ -422,9 +422,9 @@
 		mixin SimpleClass;
 		AST ppTest(string pmVar) {
 			auto pos = currentPosition();
 			return opAndAnd( super.ppTest(pmVar),
-				new FuncallExpression(pos, new VarExpression(pos,"=="), access(pmVar,path), e)
+				new App(pos, new Var(pos,"=="), access(pmVar,path), e)
 			);
 		}
 	}
 
@@ -444,9 +444,9 @@
 		}
 		else
 		{
 			AST e = E(0);
-			if(auto ev = cast(VarExpression)e)
+			if(auto ev = cast(Var)e)
 				if(ev.name == "_")
 					result ~= new WildPattern(path);
 				else
 					result ~= new VarPattern(path, ev.name);
@@ -463,11 +463,11 @@
 		foreach(p; pats) {
 			AST c2 = p.ppTest(pmVar);
 			if( c2 !is null )
 				cond = cond is null ? c2
-				    : new FuncallExpression(pos, new VarExpression(pos,"&&"), cond, c2);
+				    : new App(pos, new Var(pos,"&&"), cond, c2);
 		}
-		return cond is null ? new IntLiteral(currentPosition(), 1) : cond;
+		return cond is null ? new Int(currentPosition(), 1) : cond;
 	}
 
 	AST ppBind(string pmVar, SinglePattern[] pats, AST thenDoThis)
 	{
@@ -478,9 +478,9 @@
 
 	AST parseId()
 	{
 		scope(exit) lex.popFront;
-		return new StrLiteral(currentPosition(), lex.front.str);
+		return new Str(currentPosition(), lex.front.str);
 	}
 
 	AST parseLambdaAfterOpenParen(immutable LexPosition pos)
 	{
@@ -495,9 +495,9 @@
 		}
 		eat("{", "after function parameters");
 		auto funbody = Body();
 		eat("}", "after function body");
-		return new FunLiteral(pos, params, funbody);
+		return new Fun(pos, params, funbody);
 	}
 
 	Parameter parseParam()
 	{
@@ -557,9 +557,9 @@
 	}
 
 	AST doNothingExpression()
 	{
-		return new StrLiteral(currentPosition(), "(empty function body)");
+		return new Str(currentPosition(), "(empty function body)");
 	}
 
 	immutable(LexPosition) currentPosition()
 	{