Index: polemy/eval.d
==================================================================
--- polemy/eval.d
+++ polemy/eval.d
@@ -11,10 +11,11 @@
 import polemy.parse;
 import polemy.value;
 import polemy.layer;
 import polemy.value;
 import polemy.valueconv;
+import std.signals;
 
 /// Objects for maitaining global environment and evaluation of expression on it
 class Evaluator
 {
 public:
@@ -22,11 +23,12 @@
 	this() { theContext = new Table; }
 
 	/// Evaluate the AST
 	Value evalAST(AST e)
 	{
-		return macroAndEval(e, ValueLayer, theContext, OverwriteCtx)[0];
+		AST[void*] mandeCache;
+		return macroAndEval(e, ValueLayer, theContext, OverwriteCtx, mandeCache)[0];
 	}
 
 	/// Evaluate the string
 	Value evalString(S,T...)(S str, T fn_ln_cn)
 	{
@@ -154,11 +156,12 @@
 
 private:
 	// little little bit incremental macro defining version.
 	// enables @macro foo(x)=... in ... foo ..., only at the top level of the
 	// interpreter and functions. better than nothing :P
-	Tuple!(Value,AST) macroAndEval( AST e_, Layer lay, Table ctx, bool overwriteCtx=CascadeCtx )
+	Tuple!(Value,AST) macroAndEval( AST e_, Layer lay, Table ctx, bool overwriteCtx
+		, ref AST[void*] mandeCache) // [TODO] avoid assuming non-moving GC
 	{
 		assert( !isASTLayer(lay) );
 
 		AST decodeAST(Value v, LexPosition pos)
 		{
@@ -166,26 +169,40 @@
 			return polemy2d!(AST)(v, pos);
 		}
 
 		if(auto e = cast(Let)e_)
 		{
-			AST   ai = decodeAST(eval(e.init, RawMacroLayer, ctx), e.init.pos);
+			void* key = cast(void*)e.init;
+			AST ai;
+			if(auto p = key in mandeCache)
+				ai = *p;
+			else {
+				ai = decodeAST(eval(e.init, RawMacroLayer, ctx), e.init.pos);
+				mandeCache[key] = ai;
+			}
 			Value vi = eval(ai, lay, ctx);
 			
 			if( !overwriteCtx )
 				ctx = new Table(ctx, Table.Kind.NotPropagateSet);
 			string theLayer = e.layer.empty ? lay : e.layer;
 			ctx.set(e.name, theLayer, vi);
 
-			auto ave = macroAndEval( e.expr, lay, ctx, OverwriteCtx );
+			auto ave = macroAndEval( e.expr, lay, ctx, OverwriteCtx, mandeCache );
 			AST  a = new Let(e.pos, e.name, e.layer, ai, ave[1]);
 			return tuple(ave[0], a);
 		}
 		else
 		{
-			AST   a = decodeAST(eval(e_, RawMacroLayer, ctx), e_.pos);
-			Value v = eval(a, lay, ctx);
+			void* key = cast(void*)e_;
+			AST a;
+			if(auto p = key in mandeCache)
+				a = *p;
+			else {
+				a = decodeAST(eval(e_, RawMacroLayer, ctx), e_.pos);
+				mandeCache[key] = a;
+			}
+			Value v = eval(a, lay, ctx, overwriteCtx);
 			return tuple(v, a);
 		}
 	}
 
 private:
@@ -273,10 +290,11 @@
 			override hash_t toHash() {
 				return (cast(hash_t)cast(void*)ast) + (cast(hash_t)cast(void*)defCtx);
 			}
 
 			AST macroCache;
+			AST[void*] mandeCache;
 			static class MemokeyType
 			{
 				void* a; Layer b; Tuple!(string,Layer,Value)[] c;
 				hash_t toHash() {
 					hash_t h = structuralHash(a) + structuralHash(b);
@@ -296,11 +314,11 @@
 					return eval(ast.funbody, lay, ctx);
 
 				auto nonMemoizedRun = (){
 					if( macroCache is null )
 					{
-						auto va = macroAndEval(e.funbody, lay, ctx);
+						auto va = macroAndEval(e.funbody, lay, ctx, CascadeCtx, mandeCache);
 						macroCache = va[1];
 						return va[0];
 					}
 					else
 						return eval(macroCache, lay, ctx);
@@ -468,35 +486,5 @@
 	// this is a shorthand for
 	//   @macro x = fun(){} in @macro(x)
 	// so it is ok to fail, but it is really incovenient on REPL
 	assert_nothrow( e.evalString(`@macro x=fun(){}`) );
 }
-
-/*
-unittest
-{
-	assert_eq( evalString(`var fac = fun(x){
-		if(x)
-			{ x*fac(x-1); }
-		else
-			{ 1; };
-	};
-	fac(10);`).val, new IntValue(BigInt(10*9*8*5040)));
-	assert_eq( evalString(`var fib = fun(x){
-		if(x<2)
-			{ 1; }
-		else
-			{ fib(x-1) + fib(x-2); };
-	};
-	fib(5);`).val, new IntValue(BigInt(8)));
-}
-unittest
-{
-	assert_eq( evalString(`@@t = fun(x){x+1}; @t(123)`).val, new IntValue(BigInt(124)) );
-	// there was a bug that declaration in the first line of function definition
-	// cannot be recursive
-	assert_nothrow( evalString(`def foo() {
-  def bar(y) { if(y<1) {0} else {bar(0)} };
-  bar(1)
-}; foo()`) );
-}
-*/