diff --git a/README.md b/README.md
index 7e7f772..072f6c0 100644
--- a/README.md
+++ b/README.md
@@ -36,20 +36,23 @@ do { | k | set k 20; printf "k=%d\n" k; };
 
 ## Literals
 - integer
-- character
+- character `'c'`
 - small pointer
 - error
-- string
-- dictionary `#{ }`
-- array `[ ]`
-- byte array `#[ ]`
-- list `#( )`
+- string `"string"`
+- byte-string `b"string"`
+- symbol `#"symbol"`
 
 ## Basic Expressions
+- dictionary `#{ }`
+- array `#[ ]`
+- byte array `#b[ ]`
+- list `#( )`
 - function calls `( )`
-- message sends `(: )`
+- message sends `(rcv:msg arg1 ...)`
 - variable declaration `| |`
-- class variable delcarations `:: | |`
+- class variable delcarations `:: [ v1 [cv1 cv2 ...] v2 ... ] `
+- assignment `var :=  value`
 
 ## Builtin functions
 
diff --git a/lib/bigint.c b/lib/bigint.c
index d678fca..7a101be 100644
--- a/lib/bigint.c
+++ b/lib/bigint.c
@@ -4882,7 +4882,7 @@ hcl_oop_t hcl_inttostr (hcl_t* hcl, hcl_oop_t num, int flagged_radix)
 			hcl->inttostr.xbuf.len = xlen;
 			return hcl->_nil;
 		}
-		return hcl_makestring(hcl, xbuf, xlen, 0);
+		return hcl_makestring(hcl, xbuf, xlen);
 	}
 
 	as = HCL_OBJ_GET_SIZE(num);
@@ -4931,7 +4931,7 @@ hcl_oop_t hcl_inttostr (hcl_t* hcl, hcl_oop_t num, int flagged_radix)
 		return hcl->_nil;
 	}
 
-	return hcl_makestring(hcl, xbuf, xlen, 0);
+	return hcl_makestring(hcl, xbuf, xlen);
 
 oops_einval:
 	hcl_seterrnum (hcl, HCL_EINVAL);
diff --git a/lib/comp.c b/lib/comp.c
index e7f965d..27e2459 100644
--- a/lib/comp.c
+++ b/lib/comp.c
@@ -2695,7 +2695,7 @@ static HCL_INLINE int compile_class_p1 (hcl_t* hcl)
 
 		/* set starting point past the added space (+1 to index, -1 to length) */
 		adj = (hcl->c->tv.s.ptr[vardcl.ivar_start] == ' ');
-		tmp = hcl_makestring(hcl, &hcl->c->tv.s.ptr[vardcl.ivar_start + adj], vardcl.ivar_len - adj, 0);
+		tmp = hcl_makestring(hcl, &hcl->c->tv.s.ptr[vardcl.ivar_start + adj], vardcl.ivar_len - adj);
 		if (HCL_UNLIKELY(!tmp)) goto oops;
 		if (emit_push_literal(hcl, tmp, &cf->u._class.start_loc) <= -1) goto oops;
 	}
@@ -2713,7 +2713,7 @@ static HCL_INLINE int compile_class_p1 (hcl_t* hcl)
 		}
 
 		adj = (hcl->c->tv.s.ptr[vardcl.cvar_start] == ' ');
-		tmp = hcl_makestring(hcl, &hcl->c->tv.s.ptr[vardcl.cvar_start + adj], vardcl.cvar_len - adj, 0);
+		tmp = hcl_makestring(hcl, &hcl->c->tv.s.ptr[vardcl.cvar_start + adj], vardcl.cvar_len - adj);
 		if (HCL_UNLIKELY(!tmp)) goto oops;
 		if (emit_push_literal(hcl, tmp, &cf->u._class.start_loc) <= -1) goto oops;
 	}
@@ -4866,12 +4866,12 @@ redo:
 			goto literal;
 
 		case HCL_CNODE_STRLIT:
-			lit = hcl_makestring(hcl, HCL_CNODE_GET_TOKPTR(oprnd), HCL_CNODE_GET_TOKLEN(oprnd), 0);
+			lit = hcl_makestring(hcl, HCL_CNODE_GET_TOKPTR(oprnd), HCL_CNODE_GET_TOKLEN(oprnd));
 			if (HCL_UNLIKELY(!lit)) return -1;
 			goto literal;
 
 		case HCL_CNODE_BSTRLIT:
-			lit = hcl_makebytestring(hcl, HCL_CNODE_GET_TOKPTR(oprnd), HCL_CNODE_GET_TOKLEN(oprnd), 0);
+			lit = hcl_makebytestring(hcl, HCL_CNODE_GET_TOKPTR(oprnd), HCL_CNODE_GET_TOKLEN(oprnd));
 			if (HCL_UNLIKELY(!lit)) return -1;
 			goto literal;
 
diff --git a/lib/dic.c b/lib/dic.c
index 5bdcd54..b4f70bb 100644
--- a/lib/dic.c
+++ b/lib/dic.c
@@ -65,7 +65,7 @@ static hcl_oop_oop_t expand_bucket (hcl_t* hcl, hcl_oop_oop_t oldbuc)
 	}
 
 	hcl_pushvolat (hcl, (hcl_oop_t*)&oldbuc);
-	newbuc = (hcl_oop_oop_t)hcl_makearray (hcl, newsz, 0);
+	newbuc = (hcl_oop_oop_t)hcl_makearray(hcl, newsz);
 	hcl_popvolat (hcl);
 	if (!newbuc) return HCL_NULL;
 
@@ -467,7 +467,7 @@ hcl_oop_t hcl_makedic (hcl_t* hcl, hcl_oow_t inisize)
 		obj->tally = HCL_SMOOI_TO_OOP(0);
 
 		hcl_pushvolat (hcl, (hcl_oop_t*)&obj);
-		bucket = (hcl_oop_oop_t)hcl_makearray(hcl, inisize, 0);
+		bucket = (hcl_oop_oop_t)hcl_makearray(hcl, inisize);
 		hcl_popvolat (hcl);
 
 		if (!bucket) obj = HCL_NULL;
diff --git a/lib/exec.c b/lib/exec.c
index 42c176b..0043414 100644
--- a/lib/exec.c
+++ b/lib/exec.c
@@ -2453,7 +2453,7 @@ static int do_throw_with_internal_errmsg (hcl_t* hcl, hcl_ooi_t ip)
 {
 	hcl_oop_t ex;
 /* TODO: consider throwing an exception object instead of a string? */
-	ex = hcl_makestring(hcl, hcl->errmsg.buf, hcl->errmsg.len, 0); /* TODO: include error location in the message? */
+	ex = hcl_makestring(hcl, hcl->errmsg.buf, hcl->errmsg.len); /* TODO: include error location in the message? */
 	if (HCL_UNLIKELY(!ex)) return -1;
 	if (do_throw(hcl, ex, ip) <= -1) return -1;
 	return 0;
@@ -4051,7 +4051,7 @@ hcl_logbfmt (hcl, HCL_LOG_STDERR, ">>>%O c->sc=%O sc=%O b2=%d b3=%d nivars=%d nc
 			case HCL_CODE_CLASS_CIMSTORE:
 			{
 				hcl_oop_t _class;
-				hcl_oop_t mdic, cons, blk, car, cdr, name;
+				hcl_oop_t mdic, blk, name;
 				int mtype;
 				static hcl_bch_t* pfx[] = { "c", "i", "ci" };
 
@@ -4464,8 +4464,7 @@ hcl_logbfmt (hcl, HCL_LOG_STDERR, ">>>%O c->sc=%O sc=%O b2=%d b3=%d nivars=%d nc
 				LOG_INST_1 (hcl, "make_array %zu", b1);
 
 				/* create an empty array */
-				/*t = hcl_makearray(hcl, b1, 0);*/
-				t = hcl_instantiate(hcl, hcl->c_array, HCL_NULL, b1);
+				t = hcl_makearray(hcl, b1);
 				if (HCL_UNLIKELY(!t)) goto oops_with_errmsg_supplement;
 
 				HCL_STACK_PUSH (hcl, t); /* push the array created */
@@ -4499,8 +4498,7 @@ hcl_logbfmt (hcl, HCL_LOG_STDERR, ">>>%O c->sc=%O sc=%O b2=%d b3=%d nivars=%d nc
 				LOG_INST_1 (hcl, "make_bytearray %zu", b1);
 
 				/* create an empty array */
-				/*t = hcl_makebytearray(hcl, HCL_NULL, b1);*/
-				t = hcl_instantiate(hcl, hcl->c_byte_array, HCL_NULL, b1);
+				t = hcl_makebytearray(hcl, HCL_NULL, b1);
 				if (HCL_UNLIKELY(!t)) goto oops_with_errmsg_supplement;
 
 				HCL_STACK_PUSH (hcl, t); /* push the byte array created */
diff --git a/lib/gc.c b/lib/gc.c
index a62f1ad..baeb270 100644
--- a/lib/gc.c
+++ b/lib/gc.c
@@ -315,7 +315,7 @@ static kernel_class_info_t kernel_classes[__KCI_MAX__] =
 		"Symbol",
 		KCI_STRING,
 		HCL_BRAND_SYMBOL,
-		HCL_CLASS_SELFSPEC_FLAG_FINAL | HCL_CLASS_SELFSPEC_FLAG_LIMITED,
+		HCL_CLASS_SELFSPEC_FLAG_FINAL | HCL_CLASS_SELFSPEC_FLAG_LIMITED, /* TODO: these flags not implemented yet */
 		0,
 		0,
 		HCL_CLASS_SPEC_FLAG_INDEXED | HCL_CLASS_SPEC_FLAG_IMMUTABLE,
@@ -1416,18 +1416,16 @@ hcl_oop_t hcl_shallowcopy (hcl_t* hcl, hcl_oop_t oop)
 static hcl_oop_class_t alloc_kernel_class (hcl_t* hcl, int class_flags, hcl_oow_t num_classvars, hcl_oow_t spec, hcl_ooi_t nivars_super, int ibrand)
 {
 	hcl_oop_class_t c;
-#if 0
 	hcl_ooi_t cspec;
-#endif
 
 	c = (hcl_oop_class_t)hcl_allocoopobj(hcl, HCL_BRAND_CLASS, HCL_CLASS_NAMED_INSTVARS + num_classvars);
 	if (HCL_UNLIKELY(!c)) return HCL_NULL;
 
 	HCL_OBJ_SET_FLAGS_KERNEL (c, HCL_OBJ_FLAGS_KERNEL_IMMATURE);
 
-#if 0 /* TODO extend the flags and uncomment this part */
 	cspec = kernel_classes[KCI_CLASS].class_spec_flags;
 	if (HCL_CLASS_SPEC_IS_IMMUTABLE(cspec)) HCL_OBJ_SET_FLAGS_RDONLY (c, 1); /* just for completeness of code. will never be true as it's not defined in the kernel class info table */
+#if 0 /* TODO extend the flags and uncomment this part */
 	if (HCL_CLASS_SPEC_IS_UNCOPYABLE(cspec)) HCL_OBJ_SET_FLAGS_UNCOPYABLE (c, 1); /* class itself is uncopyable */
 #endif
 
diff --git a/lib/hcl.h b/lib/hcl.h
index e269cd7..212c605 100644
--- a/lib/hcl.h
+++ b/lib/hcl.h
@@ -359,22 +359,22 @@ typedef enum hcl_obj_type_t hcl_obj_type_t;
  * size calculation and the access to the payload fields become more complex.
  * Therefore, i've dropped the idea.
  * ========================================================================= */
-#define HCL_OBJ_FLAGS_TYPE_BITS      (6)
-#define HCL_OBJ_FLAGS_UNIT_BITS      (5)
-#define HCL_OBJ_FLAGS_EXTRA_BITS     (1)
-#define HCL_OBJ_FLAGS_KERNEL_BITS    (2)
-#define HCL_OBJ_FLAGS_MOVED_BITS     (2)
-#define HCL_OBJ_FLAGS_NGC_BITS       (1)
-#define HCL_OBJ_FLAGS_TRAILER_BITS   (1)
-#define HCL_OBJ_FLAGS_SYNCODE_BITS   (5)
-#define HCL_OBJ_FLAGS_BRAND_BITS     (6)
-#define HCL_OBJ_FLAGS_FLEXI_BITS     (1)
+#define HCL_OBJ_FLAGS_TYPE_BITS      (6) /* 6 */
+#define HCL_OBJ_FLAGS_UNIT_BITS      (5) /* 11 */
+#define HCL_OBJ_FLAGS_EXTRA_BITS     (1) /* 12 */
+#define HCL_OBJ_FLAGS_KERNEL_BITS    (2) /* 14 */
+#define HCL_OBJ_FLAGS_MOVED_BITS     (2) /* 16 */
+#define HCL_OBJ_FLAGS_NGC_BITS       (1) /* 17 */
+#define HCL_OBJ_FLAGS_TRAILER_BITS   (1) /* 18 */
+#define HCL_OBJ_FLAGS_SYNCODE_BITS   (5) /* 23 */
+#define HCL_OBJ_FLAGS_BRAND_BITS     (6) /* 29 */
+#define HCL_OBJ_FLAGS_FLEXI_BITS     (1) /* 30 */
+#define HCL_OBJ_FLAGS_RDONLY_BITS    (1) /* 31 */
 
 /*
 #define HCL_OBJ_FLAGS_PERM_BITS       1
 #define HCL_OBJ_FLAGS_MOVED_BITS      2
 #define HCL_OBJ_FLAGS_PROC_BITS       2
-#define HCL_OBJ_FLAGS_RDONLY_BITS     1
 #define HCL_OBJ_FLAGS_GCFIN_BITS      4
 #define HCL_OBJ_FLAGS_TRAILER_BITS    1
 #define HCL_OBJ_FLAGS_HASH_BITS       2
@@ -390,7 +390,8 @@ typedef enum hcl_obj_type_t hcl_obj_type_t;
 #define HCL_OBJ_FLAGS_TRAILER_SHIFT     (HCL_OBJ_FLAGS_SYNCODE_BITS   + HCL_OBJ_FLAGS_SYNCODE_SHIFT)
 #define HCL_OBJ_FLAGS_SYNCODE_SHIFT     (HCL_OBJ_FLAGS_BRAND_BITS     + HCL_OBJ_FLAGS_BRAND_SHIFT)
 #define HCL_OBJ_FLAGS_BRAND_SHIFT       (HCL_OBJ_FLAGS_FLEXI_BITS     + HCL_OBJ_FLAGS_FLEXI_SHIFT)
-#define HCL_OBJ_FLAGS_FLEXI_SHIFT       (0)
+#define HCL_OBJ_FLAGS_FLEXI_SHIFT       (HCL_OBJ_FLAGS_RDONLY_BITS    + HCL_OBJ_FLAGS_RDONLY_SHIFT)
+#define HCL_OBJ_FLAGS_RDONLY_SHIFT      (0)
 
 #define HCL_OBJ_GET_FLAGS_TYPE(oop)        HCL_GETBITS(hcl_oow_t, (oop)->_flags, HCL_OBJ_FLAGS_TYPE_SHIFT,      HCL_OBJ_FLAGS_TYPE_BITS)
 #define HCL_OBJ_GET_FLAGS_UNIT(oop)        HCL_GETBITS(hcl_oow_t, (oop)->_flags, HCL_OBJ_FLAGS_UNIT_SHIFT,      HCL_OBJ_FLAGS_UNIT_BITS)
@@ -402,6 +403,7 @@ typedef enum hcl_obj_type_t hcl_obj_type_t;
 #define HCL_OBJ_GET_FLAGS_SYNCODE(oop)     HCL_GETBITS(hcl_oow_t, (oop)->_flags, HCL_OBJ_FLAGS_SYNCODE_SHIFT,   HCL_OBJ_FLAGS_SYNCODE_BITS)
 #define HCL_OBJ_GET_FLAGS_BRAND(oop)       HCL_GETBITS(hcl_oow_t, (oop)->_flags, HCL_OBJ_FLAGS_BRAND_SHIFT,     HCL_OBJ_FLAGS_BRAND_BITS)
 #define HCL_OBJ_GET_FLAGS_FLEXI(oop)       HCL_GETBITS(hcl_oow_t, (oop)->_flags, HCL_OBJ_FLAGS_FLEXI_SHIFT,     HCL_OBJ_FLAGS_FLEXI_BITS)
+#define HCL_OBJ_GET_FLAGS_RDONLY(oop)      HCL_GETBITS(hcl_oow_t, (oop)->_flags, HCL_OBJ_FLAGS_RDONLY_SHIFT,    HCL_OBJ_FLAGS_RDONLY_BITS)
 
 #define HCL_OBJ_SET_FLAGS_TYPE(oop,v)      HCL_SETBITS(hcl_oow_t, (oop)->_flags, HCL_OBJ_FLAGS_TYPE_SHIFT,      HCL_OBJ_FLAGS_TYPE_BITS,      v)
 #define HCL_OBJ_SET_FLAGS_UNIT(oop,v)      HCL_SETBITS(hcl_oow_t, (oop)->_flags, HCL_OBJ_FLAGS_UNIT_SHIFT,      HCL_OBJ_FLAGS_UNIT_BITS,      v)
@@ -413,6 +415,7 @@ typedef enum hcl_obj_type_t hcl_obj_type_t;
 #define HCL_OBJ_SET_FLAGS_SYNCODE(oop,v)   HCL_SETBITS(hcl_oow_t, (oop)->_flags, HCL_OBJ_FLAGS_SYNCODE_SHIFT,   HCL_OBJ_FLAGS_SYNCODE_BITS,   v)
 #define HCL_OBJ_SET_FLAGS_BRAND(oop,v)     HCL_SETBITS(hcl_oow_t, (oop)->_flags, HCL_OBJ_FLAGS_BRAND_SHIFT,     HCL_OBJ_FLAGS_BRAND_BITS,     v)
 #define HCL_OBJ_SET_FLAGS_FLEXI(oop,v)     HCL_SETBITS(hcl_oow_t, (oop)->_flags, HCL_OBJ_FLAGS_FLEXI_SHIFT,     HCL_OBJ_FLAGS_FLEXI_BITS, v)
+#define HCL_OBJ_SET_FLAGS_RDONLY(oop,v)    HCL_SETBITS(hcl_oow_t, (oop)->_flags, HCL_OBJ_FLAGS_RDONLY_SHIFT,    HCL_OBJ_FLAGS_RDONLY_BITS, v)
 
 #define HCL_OBJ_GET_SIZE(oop) ((oop)->_size)
 #define HCL_OBJ_GET_CLASS(oop) ((oop)->_class)
@@ -2859,8 +2862,7 @@ HCL_EXPORT hcl_oop_t hcl_makecons (
 
 HCL_EXPORT hcl_oop_t hcl_makearray (
 	hcl_t*     hcl,
-	hcl_oow_t  size,
-	int        ngc
+	hcl_oow_t  len
 );
 
 HCL_EXPORT hcl_oop_t hcl_makebytearray (
@@ -2872,22 +2874,19 @@ HCL_EXPORT hcl_oop_t hcl_makebytearray (
 HCL_EXPORT hcl_oop_t hcl_makebytestringwithbytes (
 	hcl_t*           hcl,
 	const hcl_oob_t* ptr,
-	hcl_oow_t        len,
-	int              ngc
+	hcl_oow_t        len
 );
 
 HCL_EXPORT hcl_oop_t hcl_makebytestring (
 	hcl_t*            hcl,
 	const hcl_ooch_t* ptr,
-	hcl_oow_t         len,
-	int               ngc
+	hcl_oow_t         len
 );
 
 HCL_EXPORT hcl_oop_t hcl_makestring (
 	hcl_t*            hcl,
 	const hcl_ooch_t* ptr,
-	hcl_oow_t         len,
-	int               ngc
+	hcl_oow_t         len
 );
 
 HCL_EXPORT hcl_oop_t hcl_makefpdec (
diff --git a/lib/obj.c b/lib/obj.c
index cee6efb..df336af 100644
--- a/lib/obj.c
+++ b/lib/obj.c
@@ -136,7 +136,7 @@ static HCL_INLINE hcl_oop_t alloc_oop_array (hcl_t* hcl, int brand, hcl_oow_t si
 
 	hdr->_flags = HCL_OBJ_MAKE_FLAGS(HCL_OBJ_TYPE_OOP, HCL_SIZEOF(hcl_oop_t), 0, 0, 0, ngc, 0, 0);
 	HCL_OBJ_SET_SIZE (hdr, size);
-	/*HCL_OBJ_SET_CLASS (hdr, hcl->_nil);*/
+	HCL_OBJ_SET_CLASS (hdr, hcl->_nil);
 	HCL_OBJ_SET_FLAGS_BRAND (hdr, brand);
 
 	while (size > 0) hdr->slot[--size] = hcl->_nil;
@@ -294,30 +294,32 @@ hcl_oop_t hcl_hatchnil (hcl_t* hcl)
 
 hcl_oop_t hcl_makebigint (hcl_t* hcl, int brand, const hcl_liw_t* ptr, hcl_oow_t len)
 {
-	hcl_oop_t oop;
+	hcl_oop_t v;
 
+/* TODO: use hcl_instantiate.. */
 	HCL_ASSERT (hcl, brand == HCL_BRAND_PBIGINT || brand == HCL_BRAND_NBIGINT);
 
 #if (HCL_LIW_BITS == HCL_OOW_BITS)
-	oop = hcl_allocwordobj(hcl, brand, ptr, len);
+	v = hcl_allocwordobj(hcl, brand, ptr, len);
 #elif (HCL_LIW_BITS == HCL_OOHW_BITS)
-	oop = hcl_allochalfwordobj(hcl, brand, ptr, len);
+	v = hcl_allochalfwordobj(hcl, brand, ptr, len);
 #else
 #	error UNSUPPORTED LIW BIT SIZE
 #endif
-	if (HCL_UNLIKELY(oop))
+	if (HCL_UNLIKELY(v))
 	{
 		hcl_oop_class_t _class = (brand == HCL_BRAND_PBIGINT)?
 			hcl->c_large_positive_integer: hcl->c_large_negative_integer;
-		HCL_OBJ_SET_FLAGS_BRAND (oop, brand);
-		HCL_OBJ_SET_CLASS (oop, (hcl_oop_t)_class);
+		HCL_OBJ_SET_FLAGS_BRAND (v, brand);
+		HCL_OBJ_SET_CLASS (v, (hcl_oop_t)_class);
 	}
-	return oop;
+	return v;
 }
 
 hcl_oop_t hcl_makecons (hcl_t* hcl, hcl_oop_t car, hcl_oop_t cdr)
 {
 /* TODO: use hcl_instantiate() */
+#if 0
 	hcl_oop_cons_t cons;
 
 	hcl_pushvolat (hcl, &car);
@@ -334,28 +336,67 @@ hcl_oop_t hcl_makecons (hcl_t* hcl, hcl_oop_t car, hcl_oop_t cdr)
 	hcl_popvolats (hcl, 2);
 
 	return (hcl_oop_t)cons;
+#else
+	hcl_oop_cons_t v;
+	hcl_pushvolat (hcl, &car);
+	hcl_pushvolat (hcl, &cdr);
+	v = (hcl_oop_cons_t)hcl_instantiate(hcl, hcl->c_cons, HCL_NULL, 0);
+	hcl_popvolats (hcl, 2);
+	if (HCL_UNLIKELY(!v))
+	{
+		const hcl_ooch_t* orgmsg = hcl_backuperrmsg(hcl);
+		hcl_seterrbfmt (hcl, HCL_ERRNUM(hcl), "unable to make cons - %js", orgmsg);
+	}
+	else
+	{
+		v->car = car;
+		v->cdr = cdr;
+	}
+	return (hcl_oop_t)v;
+#endif
 }
 
-hcl_oop_t hcl_makearray (hcl_t* hcl, hcl_oow_t size, int ngc)
+hcl_oop_t hcl_makearray (hcl_t* hcl, hcl_oow_t len)
 {
-/* TODO: use hcl_instantiate() */
+#if 0
 	hcl_oop_t v;
 	v = hcl_allocoopobj(hcl, HCL_BRAND_ARRAY, size);
 	if (HCL_LIKELY(v)) HCL_OBJ_SET_CLASS (v, (hcl_oop_t)hcl->c_array);
 	return v;
+#else
+	hcl_oop_t v;
+	v = hcl_instantiate(hcl, hcl->c_array, HCL_NULL, len);
+	if (HCL_UNLIKELY(!v))
+	{
+		const hcl_ooch_t* orgmsg = hcl_backuperrmsg(hcl);
+		hcl_seterrbfmt (hcl, HCL_ERRNUM(hcl), "unable to make array - %js", orgmsg);
+	}
+	return v;
+#endif
 }
 
-hcl_oop_t hcl_makebytearray (hcl_t* hcl, const hcl_oob_t* ptr, hcl_oow_t size)
+hcl_oop_t hcl_makebytearray (hcl_t* hcl, const hcl_oob_t* ptr, hcl_oow_t len)
 {
-/* TODO: use hcl_instantiate() */
+#if 0
 	hcl_oop_t v;
 	v = hcl_allocbyteobj(hcl, HCL_BRAND_BYTE_ARRAY, ptr, size);
 	if (HCL_LIKELY(v)) HCL_OBJ_SET_CLASS (v, (hcl_oop_t)hcl->c_byte_array);
 	return v;
+#else
+	hcl_oop_t v;
+	v = hcl_instantiate(hcl, hcl->c_byte_array, ptr, len);
+	if (HCL_UNLIKELY(!v))
+	{
+		const hcl_ooch_t* orgmsg = hcl_backuperrmsg(hcl);
+		hcl_seterrbfmt (hcl, HCL_ERRNUM(hcl), "unable to make byte-array - %js", orgmsg);
+	}
+	return v;
+#endif
 }
 
-hcl_oop_t hcl_makebytestringwithbytes (hcl_t* hcl, const hcl_oob_t* ptr, hcl_oow_t len, int ngc)
+hcl_oop_t hcl_makebytestringwithbytes (hcl_t* hcl, const hcl_oob_t* ptr, hcl_oow_t len)
 {
+#if 0
 	hcl_oop_byte_t b;
 	hcl_oow_t i;
 	hcl_oob_t v;
@@ -378,10 +419,21 @@ hcl_oop_t hcl_makebytestringwithbytes (hcl_t* hcl, const hcl_oob_t* ptr, hcl_oow
 	}
 
 	return (hcl_oop_t)b;
+#else
+	hcl_oop_byte_t v;
+	v = (hcl_oop_byte_t)hcl_instantiate(hcl, hcl->c_byte_string, ptr, len);
+	if (HCL_UNLIKELY(!v))
+	{
+		const hcl_ooch_t* orgmsg = hcl_backuperrmsg(hcl);
+		hcl_seterrbfmt (hcl, HCL_ERRNUM(hcl), "unable to make byte-string with bytes - %js", orgmsg);
+	}
+	return (hcl_oop_t)v;
+#endif
 }
 
-hcl_oop_t hcl_makebytestring (hcl_t* hcl, const hcl_ooch_t* ptr, hcl_oow_t len, int ngc)
+hcl_oop_t hcl_makebytestring (hcl_t* hcl, const hcl_ooch_t* ptr, hcl_oow_t len)
 {
+#if 0
 	/* a byte string is a byte array with an extra null at the back.
 	 * the input to this function, however, is the pointer to hcl_ooch_t data
 	 * because this function is mainly used to convert a token to a byte string.
@@ -409,10 +461,33 @@ hcl_oop_t hcl_makebytestring (hcl_t* hcl, const hcl_ooch_t* ptr, hcl_oow_t len,
 	}
 
 	return (hcl_oop_t)b;
+#else
+	hcl_oop_byte_t v;
+
+	v = (hcl_oop_byte_t)hcl_instantiate(hcl, hcl->c_byte_string, HCL_NULL, len);
+	if (HCL_UNLIKELY(!v))
+	{
+		const hcl_ooch_t* orgmsg = hcl_backuperrmsg(hcl);
+		hcl_seterrbfmt (hcl, HCL_ERRNUM(hcl), "unable to make bytestring - %js", orgmsg);
+	}
+	else
+	{
+		hcl_oow_t i;
+		hcl_oob_t b;
+		for (i = 0; i < len; i++)
+		{
+			b = ptr[i] & 0xFF;
+			HCL_OBJ_SET_BYTE_VAL(v, i, b);
+		}
+	}
+
+	return (hcl_oop_t)v;
+#endif
 }
 
-hcl_oop_t hcl_makestring (hcl_t* hcl, const hcl_ooch_t* ptr, hcl_oow_t len, int ngc)
+hcl_oop_t hcl_makestring (hcl_t* hcl, const hcl_ooch_t* ptr, hcl_oow_t len)
 {
+#if 0
 	hcl_oop_char_t c;
 	/*c = hcl_alloccharobj(hcl, HCL_BRAND_STRING, ptr, len);*/
 	c = (hcl_oop_char_t)alloc_numeric_array(hcl, HCL_BRAND_STRING, ptr, len, HCL_OBJ_TYPE_CHAR, HCL_SIZEOF(hcl_ooch_t), 1, ngc);
@@ -426,6 +501,16 @@ hcl_oop_t hcl_makestring (hcl_t* hcl, const hcl_ooch_t* ptr, hcl_oow_t len, int
 		HCL_OBJ_SET_CLASS (c, (hcl_oop_t)hcl->c_string);
 	}
 	return (hcl_oop_t)c;
+#else
+	hcl_oop_t v;
+	v = hcl_instantiate(hcl, hcl->c_string, ptr, len);
+	if (HCL_UNLIKELY(!v))
+	{
+		const hcl_ooch_t* orgmsg = hcl_backuperrmsg(hcl);
+		hcl_seterrbfmt (hcl, HCL_ERRNUM(hcl), "unable to make string - %js", orgmsg);
+	}
+	return v;
+#endif
 }
 
 hcl_oop_t hcl_makefpdec (hcl_t* hcl, hcl_oop_t value, hcl_ooi_t scale)
@@ -656,13 +741,11 @@ hcl_oop_t hcl_instantiate (hcl_t* hcl, hcl_oop_class_t _class, const void* vptr,
 
 	if (HCL_LIKELY(oop))
 	{
-	#if 0
 		hcl_ooi_t spec;
-	#endif
 		HCL_OBJ_SET_CLASS (oop, (hcl_oop_t)_class);
-	#if 0 /* TODO: revive this part */
 		spec = HCL_OOP_TO_SMOOI(_class->spec);
 		if (HCL_CLASS_SPEC_IS_IMMUTABLE(spec)) HCL_OBJ_SET_FLAGS_RDONLY (oop, 1);
+	#if 0 /* TODO: revive this part */
 		if (HCL_CLASS_SPEC_IS_UNCOPYABLE(spec)) HCL_OBJ_SET_FLAGS_UNCOPYABLE (oop, 1);
 	#endif
 		HCL_OBJ_SET_FLAGS_BRAND(oop, HCL_OOP_TO_SMOOI(_class->ibrand));
@@ -727,13 +810,11 @@ hcl_oop_t hcl_instantiatewithtrailer (hcl_t* hcl, hcl_oop_class_t _class, hcl_oo
 
 	if (HCL_LIKELY(oop))
 	{
-	#if 0
 		hcl_ooi_t spec;
-	#endif
 		HCL_OBJ_SET_CLASS (oop, (hcl_oop_t)_class);
-	#if 0 /* TODO: revive this part */
 		spec = HCL_OOP_TO_SMOOI(_class->spec);
 		if (HCL_CLASS_SPEC_IS_IMMUTABLE(spec)) HCL_OBJ_SET_FLAGS_RDONLY (oop, 1);
+	#if 0 /* TODO: revive this part */
 		/* the object with trailer is to to uncopyable in hcl_allocoopobjwithtrailer() so no need to check/set it again here
 		if (HCL_CLASS_SPEC_IS_UNCOPYABLE(spec)) HCL_OBJ_SET_FLAGS_UNCOPYABLE (oop, 1);
 		*/
diff --git a/lib/prim.c b/lib/prim.c
index b8a99ca..f17cc3d 100644
--- a/lib/prim.c
+++ b/lib/prim.c
@@ -204,7 +204,7 @@ static hcl_pfrc_t pf_sprintf (hcl_t* hcl, hcl_mod_t* mod, hcl_ooi_t nargs)
 	else
 	{
 		hcl_oop_t str;
-		str = hcl_makestring(hcl, hcl->sprintf.xbuf.ptr, hcl->sprintf.xbuf.len, 0);
+		str = hcl_makestring(hcl, hcl->sprintf.xbuf.ptr, hcl->sprintf.xbuf.len);
 		if (!str) return HCL_PF_FAILURE;
 
 		HCL_STACK_SETRET (hcl, nargs, str);
@@ -487,7 +487,7 @@ static hcl_pfrc_t pf_gets (hcl_t* hcl, hcl_mod_t* mod, hcl_ooi_t nargs)
 		}
 		else
 		{
-			v = hcl_makestring(hcl, ptr, len, 0);
+			v = hcl_makestring(hcl, ptr, len);
 			if (ptr != buf) hcl_freemem(hcl, ptr);
 			if (HCL_UNLIKELY(!v)) return HCL_PF_FAILURE;
 		}
diff --git a/lib/sym.c b/lib/sym.c
index ef32510..38045de 100644
--- a/lib/sym.c
+++ b/lib/sym.c
@@ -59,7 +59,7 @@ static hcl_oop_oop_t expand_bucket (hcl_t* hcl, hcl_oop_oop_t oldbuc)
 	}
 
 	hcl_pushvolat (hcl, (hcl_oop_t*)&oldbuc);
-	newbuc = (hcl_oop_oop_t)hcl_makearray(hcl, newsz, 0);
+	newbuc = (hcl_oop_oop_t)hcl_makearray(hcl, newsz);
 	hcl_popvolat (hcl);
 	if (!newbuc) return HCL_NULL;
 
diff --git a/lib/xchg.c b/lib/xchg.c
index 4af95b1..00b6249 100644
--- a/lib/xchg.c
+++ b/lib/xchg.c
@@ -368,7 +368,7 @@ int hcl_unmarshalcode (hcl_t* hcl, hcl_code_t* code, hcl_xchg_reader_t rdr, void
 				}
 				nbytes = hcl_leoowtoh(w);
 
-				ns = hcl_makestring(hcl, HCL_NULL, nchars, 0);
+				ns = hcl_makestring(hcl, HCL_NULL, nchars);
 				if (HCL_UNLIKELY(!ns)) goto oops;
 
 				ucspos = 0;
diff --git a/mod/core.c b/mod/core.c
index 3706f65..e20af76 100644
--- a/mod/core.c
+++ b/mod/core.c
@@ -181,6 +181,12 @@ static hcl_pfrc_t __basic_at_put (hcl_t* hcl, hcl_mod_t* mod, hcl_ooi_t nargs, i
 		return HCL_PF_FAILURE;
 	}
 
+	if (HCL_OBJ_GET_FLAGS_RDONLY(obj))
+	{
+		hcl_seterrbfmt (hcl, HCL_EINVAL, "receiver immutable - %O", obj);
+		return HCL_PF_FAILURE;
+	}
+
 	if (hcl_inttooow_noseterr(hcl, pos, &index) <= 0)
 	{
 		/* negative integer or not integer */
@@ -189,9 +195,10 @@ static hcl_pfrc_t __basic_at_put (hcl_t* hcl, hcl_mod_t* mod, hcl_ooi_t nargs, i
 	}
 
 	_class = (hcl_oop_class_t)HCL_CLASSOF(hcl, obj);
-	if (span_fixed)
+	if (span_fixed) /* include the fixed part in positioning */
 	{
 		hcl_oow_t size;
+
 		size = HCL_OBJ_GET_SIZE(obj);
 		if (index >= size)
 		{
diff --git a/t/Makefile.am b/t/Makefile.am
index e3f6296..e2ab1c5 100644
--- a/t/Makefile.am
+++ b/t/Makefile.am
@@ -32,7 +32,7 @@ TESTS = $(check_PROGRAMS) $(check_SCRIPTS) $(check_ERRORS)
 
 TEST_EXTENSIONS = .hcl .err
 
-HCLBIN = ../bin/hcl
+HCLBIN = $(top_builddir)/bin/hcl
 
 HCL_LOG_COMPILER = $(SHELL) $(abs_srcdir)/run.sh $(HCLBIN) --modlibdirs="@abs_top_builddir@/mod:@abs_top_builddir@/mod/.libs" --heapsize=0
 AM_HCL_LOG_FLAGS =
diff --git a/t/Makefile.in b/t/Makefile.in
index 765eae4..d184e59 100644
--- a/t/Makefile.in
+++ b/t/Makefile.in
@@ -497,7 +497,7 @@ check_ERRORS = \
 
 EXTRA_DIST = $(check_SCRIPTS) $(check_ERRORS)
 TEST_EXTENSIONS = .hcl .err
-HCLBIN = ../bin/hcl
+HCLBIN = $(top_builddir)/bin/hcl
 HCL_LOG_COMPILER = $(SHELL) $(abs_srcdir)/run.sh $(HCLBIN) --modlibdirs="@abs_top_builddir@/mod:@abs_top_builddir@/mod/.libs" --heapsize=0
 AM_HCL_LOG_FLAGS = 
 ERR_LOG_COMPILER = $(SHELL) $(abs_srcdir)/err.sh $(HCLBIN) --modlibdirs="@abs_top_builddir@/mod:@abs_top_builddir@/mod/.libs" --heapsize=0