diff --git a/moo/kernel/Collect.moo b/moo/kernel/Collect.moo
index 725172c..09b7d41 100644
--- a/moo/kernel/Collect.moo
+++ b/moo/kernel/Collect.moo
@@ -314,7 +314,7 @@ class OrderedCollection(SequenceableCollection)
 	method initWithCapacity: capacity
 	{
 		self.buffer := Array new: capacity.
-		self.firstIndex := capacity div: 2.
+		self.firstIndex := capacity bitShift: -1.
 		self.lastIndex := self.firstIndex.
 	}
 
@@ -359,7 +359,7 @@ class OrderedCollection(SequenceableCollection)
 
 	method addFirst: obj
 	{
-		if (self.firstIndex == 0) { self growBy: 8 shiftBy: 8 }.
+		if (self.firstIndex == 0) { self __grow_and_shift(8, 8) }.
 		self.firstIndex := self.firstIndex - 1.
 		self.buffer at: self.firstIndex put: obj.
 		^obj.
@@ -367,7 +367,7 @@ class OrderedCollection(SequenceableCollection)
 
 	method addLast: obj
 	{
-		if (self.lastIndex == self.buffer size) { self growBy: 8 shiftBy: 0 }.
+		if (self.lastIndex == self.buffer size) { self __grow_and_shift(8, 0) }.
 		self.buffer at: self.lastIndex put: obj.
 		self.lastIndex := self.lastIndex + 1.
 		^obj.
@@ -377,7 +377,7 @@ class OrderedCollection(SequenceableCollection)
 	{
 		| coll_to_add |
 		coll_to_add := if (self == coll) { coll shallowCopy } else { coll }.
-		self ensureHeadRoom: (coll_to_add size).
+		self __ensure_head_room(coll_to_add size).
 		coll_to_add reverseDo: [:obj | 
 			self.firstIndex := self.firstIndex - 1.
 			self.buffer at: self.firstIndex put: obj.
@@ -389,7 +389,7 @@ class OrderedCollection(SequenceableCollection)
 	{
 		| coll_to_add |
 		coll_to_add := if (self == coll) { coll shallowCopy } else { coll }.
-		self ensureTailRoom: (coll_to_add size).
+		self __ensure_tail_room(coll_to_add size).
 		coll_to_add do: [:obj |
 			self.buffer at: self.lastIndex put: obj.
 			self.lastIndex := self.lastIndex + 1.
@@ -399,8 +399,14 @@ class OrderedCollection(SequenceableCollection)
 
 	method add: obj beforeIndex: index
 	{
-		self insert: obj beforeIndex: index.
-		^obj
+		self __insert_before_index(obj, index).
+		^obj.
+	}
+
+	method add: obj afterIndex: index
+	{
+		self __insert_before_index(obj, index + 1).
+		^obj.
 	}
 
 	method removeFirst
@@ -462,7 +468,7 @@ class OrderedCollection(SequenceableCollection)
 		## remove the element at the given position.
 		| obj |
 		obj := self at: index. ## the range is checed by the at: method.
-		self removeIndex:  index + self.firstIndex.
+		self __remove_Index(index + self.firstIndex).
 		^obj
 	}
 
@@ -477,7 +483,7 @@ class OrderedCollection(SequenceableCollection)
 		while (i < self.lastIndex)
 		{
 			cand := self.buffer at: i.
-			if (obj = cand) { self removeIndex: i. ^cand }.
+			if (obj = cand) { self __remove_index(i). ^cand }.
 			i := i + 1.
 		}.
 		^error_block value.
@@ -525,7 +531,7 @@ class OrderedCollection(SequenceableCollection)
 	## ------------------------------------------------
 	## PRIVATE METHODS
 	## ------------------------------------------------
-	method growBy: grow_size shiftBy: shift_count
+	method __grow_and_shift(grow_size, shift_count)
 	{
 		| newcon |
 		newcon := (self.buffer class) new: (self.buffer size + grow_size).
@@ -537,46 +543,71 @@ class OrderedCollection(SequenceableCollection)
 		self.lastIndex := self.lastIndex + shift_count.
 	}
 
-	method ensureHeadRoom: size
+	method __ensure_head_room(size)
 	{
 		| grow_size |
 		if (self.firstIndex < size)
 		{
 			grow_size := size - self.firstIndex + 8.
-			self growBy: grow_size shiftBy: grow_size.
+			self __grow_and_shift(grow_size, grow_size).
 		}
 	}
 
-	method ensureTailRoom: size
+	method __ensure_tail_room(size)
 	{
 		| tmp |
 		tmp := (self.buffer size) - self.lastIndex. ## remaining capacity
 		if (tmp < size)
 		{
-			tmp := size - tmp + 8.  ## grow by this
-			self growBy: tmp shiftBy: 0.
+			tmp := size - tmp + 8.  ## grow by this amount
+			self __grow_and_shift(tmp, 0).
 		}
 	}
 
-	method insert: obj beforeIndex: index
+	method __insert_before_index(obj, index)
 	{
-		## internal use only - index must be between 0 and self size inclusive
+		| i start pos cursize reqsize |
 
-		| i start |
-		if (self size == self.buffer size) { self growBy: 8 shiftBy: 8 }.
-		start := self.firstIndex + index.
-		i := self.lastIndex.
-		while (i > start)
+		if (index <= 0)
 		{
-			self.buffer at: i put: (self.buffer at: i - 1).
-			i := i - 1.
+			## treat a negative index as the indicator to 
+			## grow space in the front side.
+			reqsize := index * -1 + 1.
+			if (reqsize >= self.firstIndex) { self __ensure_head_room(reqsize) }.
+			self.firstIndex := self.firstIndex + index - 1.
+			self.buffer at: self.firstIndex put: obj.
+		}
+		else
+		{
+			cursize := self size.
+			if (self.firstIndex > 0 and: [index <= (cursize bitShift: -1)])
+			{
+				start := self.firstIndex - 1.
+				self.buffer replaceFrom: start to: (start + index - 1) with: self.buffer startingAt: self.firstIndex.
+				self.buffer at: (start + index)  put: obj.
+				self.firstIndex := start.
+			}
+			else
+			{
+				reqsize := if (index > cursize) { index - cursize } else { 1 }.
+				if (reqsize < 8) { reqsize := 8 }.
+				self __grow_and_shift(reqsize + 8, 0).
+
+				start := self.firstIndex + index.
+				i := self.lastIndex.
+				while (i > start)
+				{
+					self.buffer at: i put: (self.buffer at: i - 1).
+					i := i - 1.
+				}.
+				pos := index + self.firstIndex.
+				self.lastIndex := if (pos > self.lastIndex) { pos + 1 } else { self.lastIndex + 1 }.
+				self.buffer at: pos put: obj.
+			}.
 		}.
-		self.lastIndex := self.lastIndex + 1.
-		self.buffer at: index + self.firstIndex put: obj.
-		^obj
 	}
 
-	method removeIndex: index
+	method __remove_index(index)
 	{
 		## remove an element at the given index from the internal buffer's
 		## angle. as it is for internal use only, no check is performed
diff --git a/moo/lib/comp.c b/moo/lib/comp.c
index 89a3b62..a932ddf 100644
--- a/moo/lib/comp.c
+++ b/moo/lib/comp.c
@@ -105,6 +105,7 @@ static struct voca_t
 	moo_oow_t len;
 	moo_ooch_t str[11];
 } vocas[] = {
+	{  3, { 'a','n','d'                                                   } },
 	{  5, { 'b','r','e','a','k'                                           } },
 	{  5, { '#','b','y','t','e'                                           } },
 	{ 10, { '#','c','h','a','r','a','c','t','e','r'                       } },
@@ -137,6 +138,7 @@ static struct voca_t
 	{  3, { 'n','i','l'                                                   } },
 	{  3, { 'o','f','f'                                                   } },
 	{  2, { 'o','n'                                                       } },
+	{  2, { 'o','r'                                                       } },
 	{  8, { '#','p','o','i','n','t','e','r'                               } },
 	{  7, { 'p','o','o','l','d','i','c'                                   } },
 	{  8, { '#','p','o','o','l','d','i','c'                               } },
@@ -169,6 +171,7 @@ static struct voca_t
 
 enum voca_id_t
 {
+	VOCA_AND,
 	VOCA_BREAK,
 	VOCA_BYTE_S,
 	VOCA_CHARACTER_S,
@@ -201,6 +204,7 @@ enum voca_id_t
 	VOCA_NIL,
 	VOCA_OFF,
 	VOCA_ON,
+	VOCA_OR,
 	VOCA_POINTER_S,
 	VOCA_POOLDIC,
 	VOCA_POOLDIC_S,
@@ -1228,6 +1232,14 @@ static int get_ident (moo_t* moo, moo_ooci_t char_read_ahead)
 		{
 			SET_TOKEN_TYPE (moo, MOO_IOTOK_CONTINUE);
 		}
+		else if (is_token_word(moo, VOCA_AND))
+		{
+			SET_TOKEN_TYPE (moo, MOO_IOTOK_AND);
+		}
+		else if (is_token_word(moo, VOCA_OR))
+		{
+			SET_TOKEN_TYPE (moo, MOO_IOTOK_OR);
+		}
 	}
 
 	return 0;
@@ -2621,7 +2633,6 @@ static void eliminate_instructions (moo_t* moo, moo_oow_t start, moo_oow_t end)
 
 	last = moo->c->mth.code.len - 1;
 
-	
 	if (end >= last)
 	{
 		/* eliminate all instructions starting from the start index.
@@ -5494,9 +5505,17 @@ static int compile_basic_expression (moo_t* moo, const moo_oocs_t* ident, const
 	/*
 	 * basic-expression := expression-primary message-expression?
 	 */
+	moo_oow_pool_t jumptoend;
+	moo_oow_pool_chunk_t* jumptoend_chunk;
+	moo_ioloc_t expr_loc;
+	moo_oow_t i, j;
 	int to_super;
 
-	if (compile_expression_primary(moo, ident, ident_loc, ident_dotted, &to_super) <= -1) return -1;
+	expr_loc = *TOKEN_LOC(moo);
+	init_oow_pool (moo, &jumptoend);
+
+start_over:
+	if (compile_expression_primary(moo, ident, ident_loc, ident_dotted, &to_super) <= -1) goto oops;
 
 #if 0
 	if (TOKEN_TYPE(moo) != MOO_IOTOK_EOF && 
@@ -5504,18 +5523,54 @@ static int compile_basic_expression (moo_t* moo, const moo_oocs_t* ident, const
 	    TOKEN_TYPE(moo) != MOO_IOTOK_PERIOD &&
 	    TOKEN_TYPE(moo) != MOO_IOTOK_SEMICOLON)
 	{
-		if (compile_message_expression(moo, to_super) <= -1) return -1;
+		if (compile_message_expression(moo, to_super) <= -1) goto oops;
 	}
 #else
 	if (TOKEN_TYPE(moo) == MOO_IOTOK_IDENT ||
 	    TOKEN_TYPE(moo) == MOO_IOTOK_BINSEL ||
 	    TOKEN_TYPE(moo) == MOO_IOTOK_KEYWORD)
 	{
-		if (compile_message_expression(moo, to_super) <= -1) return -1;
+		if (compile_message_expression(moo, to_super) <= -1) goto oops;
 	}
 #endif
 
+
+	if (TOKEN_TYPE(moo) == MOO_IOTOK_AND)
+ 	{
+		if (add_to_oow_pool(moo, &jumptoend, moo->c->mth.code.len) <= -1 ||
+ 		    emit_single_param_instruction(moo, BCODE_JUMP_FORWARD_IF_FALSE, MAX_CODE_JUMP) <= -1 ||
+		    emit_byte_instruction(moo, BCODE_POP_STACKTOP) <= -1) goto oops;
+		GET_TOKEN (moo);
+		goto start_over;
+ 	}
+ 	else if (TOKEN_TYPE(moo) == MOO_IOTOK_OR)
+	{
+		if (add_to_oow_pool(moo, &jumptoend, moo->c->mth.code.len) <= -1 ||
+ 		    emit_single_param_instruction(moo, BCODE_JUMP_FORWARD_IF_TRUE, MAX_CODE_JUMP) <= -1 ||
+		    emit_byte_instruction(moo, BCODE_POP_STACKTOP) <= -1) goto oops;
+		GET_TOKEN (moo);
+		goto start_over;
+	}
+
+	/* patch instructions that jumps to the end of if expression */
+	for (jumptoend_chunk = jumptoend.head, i = 0; jumptoend_chunk; jumptoend_chunk = jumptoend_chunk->next)
+	{
+		/* pass expr_loc to every call to patch_long_forward_jump_instruction().
+		 * it's harmless because if the first call doesn't flood, the subseqent 
+		 * call will never flood either. */
+		for (j = 0; j < MOO_COUNTOF(jumptoend.static_chunk.buf) && i < jumptoend.count; j++)
+		{
+			if (patch_long_forward_jump_instruction (moo, jumptoend_chunk->buf[j], moo->c->mth.code.len, &expr_loc) <= -1) goto oops;
+			i++;
+		}
+	}
+
+	fini_oow_pool (moo, &jumptoend);
 	return 0;
+
+oops:
+	fini_oow_pool (moo, &jumptoend);
+	return -1;
 }
 
 static int compile_braced_block (moo_t* moo)
diff --git a/moo/lib/exec.c b/moo/lib/exec.c
index 9de8e24..aa299ac 100644
--- a/moo/lib/exec.c
+++ b/moo/lib/exec.c
@@ -3630,7 +3630,7 @@ static int start_method (moo_t* moo, moo_oop_method_t method, moo_oow_t nargs)
 
 #if defined(MOO_DEBUG_VM_EXEC)
 	/* set it to a fake value */
-	moo->last_instruction_pointer = 0; 
+	moo->last_inst_pointer = 0; 
 #endif
 
 	preamble = MOO_OOP_TO_SMOOI(method->preamble);
@@ -3765,7 +3765,7 @@ static int start_method (moo_t* moo, moo_oop_method_t method, moo_oow_t nargs)
 			stack_base = moo->sp - nargs - 1; /* stack base before receiver and arguments */
 
 			pfnum = MOO_METHOD_GET_PREAMBLE_INDEX(preamble);
-			LOG_INST1 (moo, "preamble_primitive %zd", pf_no);
+			LOG_INST1 (moo, "preamble_primitive %zd", pfnum);
 
 			if (pfnum >= 0 && pfnum < MOO_COUNTOF(pftab))
 			{
diff --git a/moo/lib/moo-prv.h b/moo/lib/moo-prv.h
index 765491f..3a0844a 100644
--- a/moo/lib/moo-prv.h
+++ b/moo/lib/moo-prv.h
@@ -54,7 +54,7 @@
 /*#define MOO_DEBUG_LEXER 1*/
 #define MOO_DEBUG_COMPILER 1
 #define MOO_DEBUG_VM_PROCESSOR 1
-/*#define MOO_DEBUG_VM_EXEC*/
+#define MOO_DEBUG_VM_EXEC
 #define MOO_PROFILE_VM 1
 #endif
 
@@ -353,6 +353,9 @@ enum moo_iotok_type_t
 	MOO_IOTOK_BREAK,
 	MOO_IOTOK_CONTINUE,
 
+	MOO_IOTOK_AND,
+	MOO_IOTOK_OR,
+
 	MOO_IOTOK_IDENT,
 	MOO_IOTOK_IDENT_DOTTED,
 	MOO_IOTOK_BINSEL,