Index: doc/ast.html
==================================================================
--- doc/ast.html
+++ doc/ast.html
@@ -243,12 +243,12 @@
 <dd><br><br>
 </dd>
 
 <script>explorer.outline.writeEnabled = true;</script>
 <dt><span class="decl">AST 
-<span class="currsymbol">init</span>
-<script>explorer.outline.addDecl('init');</script>
+<span class="currsymbol">vdef</span>
+<script>explorer.outline.addDecl('vdef');</script>
 
 ;
 </span></dt>
 <script>explorer.outline.writeEnabled = false;</script>
 
@@ -592,11 +592,11 @@
 
 </td></tr>
 		<tr><td id="docfooter">
 			Page was generated with
 			<img src="candydoc/img/candydoc.gif" style="vertical-align:middle; position:relative; top:-1px">
-			on Sat Nov 27 01:17:56 2010
+			on Sat Nov 27 21:45:06 2010
 
 		</td></tr>
 	</table>
 </div>
 <script>

Index: doc/eval.html
==================================================================
--- doc/eval.html
+++ doc/eval.html
@@ -130,11 +130,11 @@
 
 </td></tr>
 		<tr><td id="docfooter">
 			Page was generated with
 			<img src="candydoc/img/candydoc.gif" style="vertical-align:middle; position:relative; top:-1px">
-			on Sat Nov 27 01:17:57 2010
+			on Sat Nov 27 21:45:07 2010
 
 		</td></tr>
 	</table>
 </div>
 <script>

Index: doc/index.html
==================================================================
--- doc/index.html
+++ doc/index.html
@@ -389,10 +389,24 @@
 <script>explorer.outline.addDecl('Layers');</script>
 
 </span></dt>
 <script>explorer.outline.writeEnabled = false;</script>
 
+ <dd><p>
+この言語の唯一の特徴的な部分は、「レイヤ」機能です。
+</p>
+
+<script>explorer.outline.incSymbolLevel();</script>
+<dl>
+<script>explorer.outline.writeEnabled = true;</script>
+<dt><span class="decl">
+<span class="currsymbol">Layers</span>
+<script>explorer.outline.addDecl('Layers');</script>
+
+</span></dt>
+<script>explorer.outline.writeEnabled = false;</script>
+
  <dd><pre>
 [Layers :: Overview]
 
   Polemy's runtime environment has many "layer"s.
   Usual execution run in the @value layer.
@@ -539,10 +553,15 @@
 
   its corresponding arguments are evaluated in the layer and passed to it.
   If you specify multiple layers, the argument expression is run multiple times.
   If you do not specify any layer for a parameter, it works in the neutral layer.
 </pre>
+</dd>
+</dl>
+<script>explorer.outline.decSymbolLevel();</script>
+
+
 </dd>
 
 
 
 <script>explorer.outline.writeEnabled = true;</script>
@@ -935,11 +954,11 @@
 
 </td></tr>
 		<tr><td id="docfooter">
 			Page was generated with
 			<img src="candydoc/img/candydoc.gif" style="vertical-align:middle; position:relative; top:-1px">
-			on Sat Nov 27 01:54:49 2010
+			on Sat Nov 27 20:49:57 2010
 
 		</td></tr>
 	</table>
 </div>
 <script>

Index: index.dd
==================================================================
--- index.dd
+++ index.dd
@@ -285,10 +285,15 @@
 
 
 
 
 $(SECTION Layers, $(SECBODY
+<p>
+この言語の唯一の特徴的な部分は、「レイヤ」機能です。
+</p>
+$(DDOC_MEMBERS
+$(SECTION Layers, $(SECBODY
 <pre>
 [Layers :: Overview]
 
   Polemy's runtime environment has many "layer"s.
   Usual execution run in the @value layer.
@@ -435,10 +440,12 @@
 
   its corresponding arguments are evaluated in the layer and passed to it.
   If you specify multiple layers, the argument expression is run multiple times.
   If you do not specify any layer for a parameter, it works in the neutral layer.
 </pre>
+))
+)
 ))
 
 
 $(SECTION Macro Layers, $(SECBODY
 <p>

Index: polemy/ast.d
==================================================================
--- polemy/ast.d
+++ polemy/ast.d
@@ -58,11 +58,11 @@
 /// AST node for variable declaration
 class Let : AST
 {
 	string name;  ///
 	Layer  layer; ///
-	AST    init;  ///
+	AST    vdef;  ///
 	AST    expr;  ///
 
 	mixin SimpleClass;
 }
 

Index: polemy/eval.d
==================================================================
--- polemy/eval.d
+++ polemy/eval.d
@@ -183,11 +183,11 @@
 		}
 		override Value eval_( Let e, Table ctx, bool ctxMod )
 		{
 			if( !ctxMod )
 				ctx = new Table(ctx, Table.Kind.NotPropagateSet);
-			Value ri = this.eval(e.init, ctx);
+			Value ri = this.eval(e.vdef, ctx);
 			ctx.set(e.name, e.layer.empty ? layerID(): e.layer, ri);
 			return this.eval(e.expr, ctx, OverwriteCtx);
 		}
 		override Value eval_( App e, Table ctx, bool ctxMod )
 		{
@@ -201,11 +201,11 @@
 		override Value macroAndEval( AST e, Table ctx, bool ctxMod )
 		{
 			// incremental execution of let-expressions
 			if(auto le = cast(Let)e)
 			{
-				AST ai = runMacro(le.init, ctx);
+				AST ai = runMacro(le.vdef, ctx);
 
 				if( !ctxMod )
 					ctx = new Table(ctx, Table.Kind.NotPropagateSet);
 
 				Value vi = this.eval(ai, ctx);
@@ -241,11 +241,16 @@
 		}
 		override Value eval_( Var e, Table ctx, bool ctxMod )
 		{
 			if( ctx.has(e.name, layerID()) )
 				return ctx.get(e.name, layerID());
-			return this.lift(ctx.get(e.name, ValueLayer, e.pos), ctx, e.pos);
+			Value v;
+			try { v = ctx.get(e.name, ValueLayer, e.pos); }
+			catch ( RuntimeException ) {
+				throw genex!RuntimeException(e.pos, e.name~" not found in layer "~layerID()~" nor "~ValueLayer);
+			}
+			return this.lift(v, ctx, e.pos);
 		}
 	}
 
 	// Macro layer. For optimization, if AST didn't change it returns null
 	class MacroLayerEval : LayerEval
@@ -284,20 +289,20 @@
 		override Value eval_( Let e, Table ctx, bool ctxMod )
 		{
 			if( !ctxMod )
 				ctx = new Table(ctx, Table.Kind.NotPropagateSet);
 
-			Value ai = this.eval(e.init, ctx);
+			Value ai = this.eval(e.vdef, ctx);
 			ctx.set(e.name, NoopLayer, null);
 			Value ae = this.eval(e.expr, ctx, OverwriteCtx);
 
 			if( ai is null && ae is null ) return null;
-			if( ai is null ) ai = ast2table(e.init);
+			if( ai is null ) ai = ast2table(e.vdef);
 			if( ae is null ) ae = ast2table(e.expr);
 
 			return ast2table(e, delegate Value (AST _){
-				if(_ is e.init) { return ai; }
+				if(_ is e.vdef) { return ai; }
 				if(_ is e.expr) { return ae; }
 				assert(false);
 			});
 		}
 		override Value eval_( App e, Table ctx, bool ctxMod )

Index: sample/macro.pmy
==================================================================
--- sample/macro.pmy
+++ sample/macro.pmy
@@ -21,12 +21,12 @@
 @macro maxGreat(x,y){@value(
 	var nx = gensym(); # generate fresh symbol
 	var ny = gensym();
 	@macro _x = @macro(nx) {name: nx};  # cheating to create {is:"Var" .. }
 	@macro _y = @macro(ny) {name: ny};  # at macro layer
-	{is: "Let", name: nx, layer: "", init: @macro(x), expr:
-		{is: "Let", name: ny, layer: "", init: @macro(y), expr:
+	{is: "Let", name: nx, layer: "", vdef: @macro(x), expr:
+		{is: "Let", name: ny, layer: "", vdef: @macro(y), expr:
 			@macro(if _x < _y then _y else _x)}} # the expression
 )};
 
 print( maxGood(print(1), print(2)) );  # 1 2 2
 print( maxBad(print(1), print(2)) );    # 1 2 2 2