diff -urN v26/Makefile v27/Makefile
--- v26/Makefile	2018-09-14 21:50:19.000000000 +0900
+++ v27/Makefile	2018-09-15 17:42:25.000000000 +0900
@@ -4,20 +4,29 @@
 CFLAGS += $(DBG)
 
 OBJS = ezyaml.o objs.o chain.o mem.o
+LIB = libezyaml.a
 TARG = ezyaml
 
 all: $(TARG)
 
 mem.c: chain.h
 objs.c: chain.h mem.h
-ezyaml.c: objs.h mem.h
-
-ezyaml: $(OBJS)
-	gcc $(CFLAGS) -o $@ $(OBJS)
+ezyaml.h: objs.h
+ezyaml.c: ezyaml.h mem.h
+ezyaml_main.c: mem.h
+
+ezyaml: ezyaml_main.o $(LIB)
+	gcc $(CFLAGS) -o $@ ezyaml_main.o $(LIB)
+
+lib: $(LIB)
+
+$(LIB): $(OBJS)
+	rm -rf $(LIB)
+	ar cq $@ $(OBJS)
 
 clean:
 	rm -f *.o *~ *.pyc
 	rm -rf __pycache__
-	rm -f $(TARG)
+	rm -f $(TARG) $(LIB)
 
 # EOF
diff -urN v26/ezyaml.c v27/ezyaml.c
--- v26/ezyaml.c	2018-09-14 22:25:48.000000000 +0900
+++ v27/ezyaml.c	2018-09-15 17:45:43.000000000 +0900
@@ -1,7 +1,7 @@
-#include "objs.h"
+#include "ezyaml.h"
 #include "mem.h"
 
-void
+static void
 err(char *t, char *s)
 {
 	fprintf(stderr, "err %s \"%s\"\n", t, s);
@@ -10,7 +10,7 @@
 
 /**/
 
-char *
+static char *
 slice_tail(char *s, int i)
 {
 	return strlen(s) >= i ? s + i : "";
@@ -18,16 +18,16 @@
 
 /**/
 
-int
+static int
 is_qts(char c)
 {
 	return c == '"' || c == '\'';
 }
 
-char *kwd_true[] = { "True", "true", "TRUE", "ON", "On", "On", NULL };
-char *kwd_false[] = { "False", "false", "FALSE", "OFF", "Off", "off", NULL };
+static char *kwd_true[] = { "True", "true", "TRUE", "ON", "On", "On", NULL };
+static char *kwd_false[] = { "False", "false", "FALSE", "OFF", "Off", "off", NULL };
 
-int
+static int
 is_any_str(char *s, char **ss)
 {
 	while(*ss){
@@ -39,14 +39,14 @@
 	return 0;
 }
 
-void
+static void
 parse_append(struct obj *buf, int c)
 {
 	char c1 = c;
 	buf_append(buf, &c1, 1);
 }
 
-void
+static void
 parse_buf_to_lst(struct obj *lst, struct obj *buf)
 {
 	parse_append(buf, '\0');
@@ -54,7 +54,7 @@
 	buf->n = 0;
 }
 
-struct obj *
+static struct obj *
 parse(char *s)
 {
 	struct obj *lst = list_new();
@@ -99,7 +99,7 @@
 	return lst;
 }
 
-int
+static int
 find_idx(char *s, char *t)
 {
 	int idx = 0;
@@ -126,7 +126,7 @@
 	return -1;
 }
 
-int
+static int
 find_colon_idx(char *s)
 {
 	int n;
@@ -140,7 +140,7 @@
 
 #define TYP_OTHER	(-1)
 
-int
+static int
 get_kind(char *s)
 {
 	if( strncmp(s, "- ", 2) == 0 ){
@@ -152,34 +152,34 @@
 	return TYP_OTHER;
 }
 
-struct obj *
+static struct obj *
 cut_tail_spc(struct obj *str)
 {
 	str_trunc(str);
 	return NULL;
 }
 
-int
+static int
 top_spc_num(char *s)
 {
 	return *s == ' ' ? 1 + top_spc_num(s+1) : 0;
 }
 
-void
+static void
 get_idt_kind(char *s, int *idt, int *kind)
 {
 	*idt = top_spc_num(s);
 	*kind = get_kind( slice_tail(s, *idt) );
 }
 
-struct obj *get_dict(int idt, struct obj *lines);
-struct obj *get_list(int idt, struct obj *lines);
-struct obj *get_other(int idt, struct obj *lines);
-struct obj *get_value(char *s);
-struct obj *get(int idt, int kind, struct obj *lines);
-char *get_cont_str(int idt, struct obj *lines);
+static struct obj *get_dict(int idt, struct obj *lines);
+static struct obj *get_list(int idt, struct obj *lines);
+static struct obj *get_other(int idt, struct obj *lines);
+static struct obj *get_value(char *s);
+static struct obj *get(int idt, int kind, struct obj *lines);
+static char *get_cont_str(int idt, struct obj *lines);
 
-struct obj *
+static struct obj *
 get_dict_v(int idt, struct obj *lines)
 {
 	char *s = lines_top_str(lines);
@@ -211,7 +211,7 @@
 	return obj_new(OBJ_TYP_PTR, &vp);
 }
 
-struct obj *
+static struct obj *
 get_dict(int idt, struct obj *lines)
 {
 	char *s = lines_pop_str(lines);
@@ -240,8 +240,7 @@
 		}
 	}else if(v->typ == OBJ_TYP_STR){
 		char *add = get_cont_str(idt+2, lines);
-		str_append(v, add);
-		free(add);
+		str_append_free(v, add);
 	}
 
 	dict_add(dic, k, v);
@@ -260,7 +259,7 @@
 	return dic;
 }
 
-struct obj *
+static struct obj *
 get_list(int idt, struct obj *lines)
 {
 	int idt_ = idt + 2;
@@ -286,7 +285,7 @@
 	return lst;
 }
 
-struct obj *
+static struct obj *
 get_value(char *s)
 {
 	int i, n;
@@ -339,7 +338,7 @@
 	return str_new_n(s, n);
 }
 
-char *
+static char *
 get_cont_str(int idt, struct obj *lines)
 {
 	if( list_len(lines) ){
@@ -364,21 +363,20 @@
 	return strdup("");
 }
 
-struct obj *
+static struct obj *
 get_other(int idt, struct obj *lines)
 {
 	char *s = lines_pop_str(lines);
 	struct obj *v = get_value( slice_tail(s, idt) );
 	if(v->typ == OBJ_TYP_STR){
 		char *add = get_cont_str(idt+2, lines);
-		str_append(v, add);
-		free(add);
+		str_append_free(v, add);
 	}
 	free(s);
 	return v;
 }
 
-struct obj *
+static struct obj *
 get(int idt, int kind, struct obj *lines)
 {
 	if(kind == OBJ_TYP_DICT){
@@ -390,7 +388,7 @@
 	return get_other(idt, lines);
 }
 
-struct obj *
+static struct obj *
 cut_comment(struct obj *str)
 {
 	char *s = obj_ptr(str);
@@ -401,7 +399,7 @@
 	return NULL;
 }
 
-int
+static int
 is_not_empty(struct obj *str)
 {
 	char *s = obj_ptr(str);
@@ -409,7 +407,7 @@
 }
 
 struct obj *
-load(struct obj *str)
+ezyaml_load(struct obj *str)
 {
 	struct obj *obj, *objs;
 	struct obj *lines = lines_new( obj_ptr(str) );
@@ -441,12 +439,12 @@
 
 /**/
 
-struct obj *dump_list(struct obj *lst, int idt);
-struct obj *dump_value(struct obj *obj, int from_dic);
-struct obj *dump_other(struct obj *obj, int idt, int from_dic);
-struct obj *dump_obj(struct obj *obj, int idt);
+static struct obj *dump_list(struct obj *lst, int idt);
+static struct obj *dump_value(struct obj *obj, int from_dic);
+static struct obj *dump_other(struct obj *obj, int idt, int from_dic);
+static struct obj *dump_obj(struct obj *obj, int idt);
 
-struct obj *
+static struct obj *
 wrap_line(struct obj *str, int idt)
 {
 	struct obj *lst;
@@ -487,7 +485,7 @@
 	return str;
 }
 
-struct obj *
+static struct obj *
 dump_dict(struct obj *dic, int idt)
 {
 	struct obj *lines = list_new();
@@ -510,8 +508,7 @@
 		}else{
 			str_append(str, " ");
 			tmp = dump_value(v, 'r');
-			str_append( str, obj_ptr(tmp) );
-			obj_del(tmp);
+			str_append_free( str, str_pop_del(tmp) );
 			str = wrap_line(str, idt);
 		}
 		list_append(lines, str);
@@ -524,7 +521,7 @@
 	return str;
 }
 
-struct obj *
+static struct obj *
 dump_list(struct obj *lst, int idt)
 {
 	struct obj *lines = list_new();
@@ -552,7 +549,7 @@
 	return str;
 }
 
-int
+static int
 is_not_same_str(char *s, struct obj *obj)
 {
 	struct obj *v = get_value(s);
@@ -561,7 +558,7 @@
 	return r;
 }
 
-int
+static int
 need_quote(char *s, struct obj *obj, int from_dic)
 {
 	char h, t;
@@ -584,7 +581,7 @@
 	return 0;
 }
 
-struct obj *
+static struct obj *
 dump_value(struct obj *obj, int from_dic)
 {
 	if(obj->typ == OBJ_TYP_STR){
@@ -637,19 +634,18 @@
 	return str_new(""); /* ! */
 }
 
-struct obj *
+static struct obj *
 dump_other(struct obj *obj, int idt, int from_dic)
 {
 	struct obj *str = dump_value(obj, from_dic);
 	char *s = cp_char_n(' ', idt);
-	s = cp_add( s, strdup( obj_ptr(str) ) );
-	obj_del(str);
+	s = cp_add( s, str_pop_del(str) );
 	str = wrap_line( str_new(s), idt);
 	free(s);
 	return str;
 }
 
-struct obj *
+static struct obj *
 dump_obj(struct obj *obj, int idt)
 {
 	int t = obj->typ;
@@ -663,35 +659,11 @@
 }
 
 struct obj *
-dump(struct obj *obj)
+ezyaml_dump(struct obj *obj)
 {
 	struct obj *str = dump_obj(obj, 0);	
 	str_append(str, "\n");
 	return str;
 }
 
-int
-main(int ac, char **av)
-{
-	struct obj *obj;
-	struct obj *str = str_read(stdin);
-	char *s;
-
-	obj = load(str);
-	obj_del(str);
-
-	str = dump(obj);
-	s = obj_ptr(str);
-	fwrite( s, 1, strlen(s), stdout );
-	obj_del(str);
-	
-	/* obj --> stderr ... */
-
-	obj_del(obj);
-
-	mem_show();
-
-	return 0;
-}
-
 /* EOF */
diff -urN v26/ezyaml.h v27/ezyaml.h
--- v26/ezyaml.h	1970-01-01 09:00:00.000000000 +0900
+++ v27/ezyaml.h	2018-09-15 12:39:56.000000000 +0900
@@ -0,0 +1,9 @@
+#ifndef __EZYAML_H__
+#define __EZYAML_H__	1
+
+#include "objs.h"
+
+struct obj *ezyaml_load(struct obj *str);
+struct obj *ezyaml_dump(struct obj *obj);
+
+#endif
diff -urN v26/ezyaml_main.c v27/ezyaml_main.c
--- v26/ezyaml_main.c	1970-01-01 09:00:00.000000000 +0900
+++ v27/ezyaml_main.c	2018-09-15 12:39:56.000000000 +0900
@@ -0,0 +1,25 @@
+#include "ezyaml.h"
+#include "mem.h"
+
+int
+main(int ac, char **av)
+{
+	char *s;
+	struct obj *str = str_read(stdin);
+	struct obj *obj = ezyaml_load(str);
+
+	obj_del(str);
+	str = ezyaml_dump(obj);
+
+	s = obj_ptr(str);
+	fwrite( s, 1, strlen(s), stdout );
+	obj_del(str);
+
+	obj_del(obj);
+
+	mem_show();
+
+	return 0;
+}
+
+/* EOF */
diff -urN v26/objs.c v27/objs.c
--- v26/objs.c	2018-09-14 21:53:22.000000000 +0900
+++ v27/objs.c	2018-09-15 17:45:43.000000000 +0900
@@ -350,6 +350,42 @@
 	return r;
 }
 
+static int
+slice_clip(int pos, int n)
+{
+	if(pos < 0){
+		pos += n;
+	}
+	pos = pos < 0 ? 0 : pos;
+	pos = pos > n ? n : pos;
+	return pos;
+}
+
+
+char *
+cp_slice(char *s, int head, int tail)
+{
+	/* free s */
+	/* tail == 0 is tail == strlen(s) */
+	int n;
+	char *r;
+
+	if(!s){
+		return NULL;
+	}
+	n = strlen(s);
+
+	head = slice_clip(head, n);
+	tail = slice_clip(tail, n);
+	if(tail == 0){
+		tail = n;
+	}
+
+	r = head < tail ? strndup(s + head, tail - head ) : strdup("");
+	free(s);
+	return r;
+}
+
 /**/
 
 struct obj *
@@ -389,9 +425,16 @@
 }
 
 void
+str_append_free(struct obj *str, char *s)
+{
+	obj_ptr(str) = cp_add( obj_ptr(str), s );
+	/* free s */
+}
+
+void
 str_append(struct obj *str, char *s)
 {
-	obj_ptr(str) = cp_add( obj_ptr(str), strdup(s) );
+	str_append_free( str, strdup(s) );
 }
 
 void
@@ -420,6 +463,15 @@
 	str_free_set( str, strdup(t) );
 }
 
+char *
+str_pop_del(struct obj *str)
+{
+	char *s = obj_ptr(str);
+	obj_ptr(str) = NULL;
+	obj_del(str);
+	return s;
+}
+
 /**/
 
 struct obj *
@@ -615,9 +667,7 @@
 	char *s = NULL;
 	struct obj *str = list_pop_top(lines);
 	if(str){
-		s = obj_ptr(str);
-		obj_ptr(str) = NULL;
-		obj_del(str);
+		s = str_pop_del(str);
 	}
 	return s;
 }
diff -urN v26/objs.h v27/objs.h
--- v26/objs.h	2018-09-14 05:09:22.000000000 +0900
+++ v27/objs.h	2018-09-15 17:45:43.000000000 +0900
@@ -71,14 +71,17 @@
 char *cp_add(char *a, char *b);
 char *cp_replace(char *s, char *from, char *to);
 char *cp_char_n(char v, int n);
+char *cp_slice(char *s, int head, int tail);
 
 struct obj *str_new(char *s);
 struct obj *str_new_n(char *s, int n);
 struct obj *str_read(FILE *fp);
 void str_free_set(struct obj *str, char *s);
+void str_append_free(struct obj *str, char *s);
 void str_append(struct obj *str, char *s);
 void str_trunc(struct obj *str);
 void str_strip(struct obj *str);
+char *str_pop_del(struct obj *str);
 
 struct obj *list_new(void);
 void list_del(struct obj *lst);