diff --git a/kavl.h b/kavl.h
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+++ b/kavl.h
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+/* The MIT License
+
+   Copyright (c) 2018 by Attractive Chaos <attractor@live.co.uk>
+
+   Permission is hereby granted, free of charge, to any person obtaining
+   a copy of this software and associated documentation files (the
+   "Software"), to deal in the Software without restriction, including
+   without limitation the rights to use, copy, modify, merge, publish,
+   distribute, sublicense, and/or sell copies of the Software, and to
+   permit persons to whom the Software is furnished to do so, subject to
+   the following conditions:
+
+   The above copyright notice and this permission notice shall be
+   included in all copies or substantial portions of the Software.
+
+   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+   EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+   MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+   NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+   BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+   ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+   CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+   SOFTWARE.
+*/
+
+/* An example:
+
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+#include "kavl.h"
+
+struct my_node {
+  char key;
+  KAVL_HEAD(struct my_node) head;
+};
+#define my_cmp(p, q) (((q)->key < (p)->key) - ((p)->key < (q)->key))
+KAVL_INIT(my, struct my_node, head, my_cmp)
+
+int main(void) {
+  const char *str = "MNOLKQOPHIA"; // from wiki, except a duplicate
+  struct my_node *root = 0;
+  int i, l = strlen(str);
+  for (i = 0; i < l; ++i) {        // insert in the input order
+    struct my_node *q, *p = malloc(sizeof(*p));
+    p->key = str[i];
+    q = kavl_insert(my, &root, p, 0);
+    if (p != q) free(p);           // if already present, free
+  }
+  kavl_itr_t(my) itr;
+  kavl_itr_first(my, root, &itr);  // place at first
+  do {                             // traverse
+    const struct my_node *p = kavl_at(&itr);
+    putchar(p->key);
+    free((void*)p);                // free node
+  } while (kavl_itr_next(my, &itr));
+  putchar('\n');
+  return 0;
+}
+*/
+
+#ifndef KAVL_H
+#define KAVL_H
+
+#ifdef __STRICT_ANSI__
+#define inline __inline__
+#endif
+
+#define KAVL_MAX_DEPTH 64
+
+#define kavl_size(head, p) ((p)? (p)->head.size : 0)
+#define kavl_size_child(head, q, i) ((q)->head.p[(i)]? (q)->head.p[(i)]->head.size : 0)
+
+#define KAVL_HEAD(__type) \
+	struct { \
+		__type *p[2]; \
+		signed char balance; /* balance factor */ \
+		unsigned size; /* #elements in subtree */ \
+	}
+
+#define __KAVL_FIND(suf, __scope, __type, __head,  __cmp) \
+	__scope __type *kavl_find_##suf(const __type *root, const __type *x, unsigned *cnt_) { \
+		const __type *p = root; \
+		unsigned cnt = 0; \
+		while (p != 0) { \
+			int cmp; \
+			cmp = __cmp(x, p); \
+			if (cmp >= 0) cnt += kavl_size_child(__head, p, 0) + 1; \
+			if (cmp < 0) p = p->__head.p[0]; \
+			else if (cmp > 0) p = p->__head.p[1]; \
+			else break; \
+		} \
+		if (cnt_) *cnt_ = cnt; \
+		return (__type*)p; \
+	}
+
+#define __KAVL_ROTATE(suf, __type, __head) \
+	/* one rotation: (a,(b,c)q)p => ((a,b)p,c)q */ \
+	static inline __type *kavl_rotate1_##suf(__type *p, int dir) { /* dir=0 to left; dir=1 to right */ \
+		int opp = 1 - dir; /* opposite direction */ \
+		__type *q = p->__head.p[opp]; \
+		unsigned size_p = p->__head.size; \
+		p->__head.size -= q->__head.size - kavl_size_child(__head, q, dir); \
+		q->__head.size = size_p; \
+		p->__head.p[opp] = q->__head.p[dir]; \
+		q->__head.p[dir] = p; \
+		return q; \
+	} \
+	/* two consecutive rotations: (a,((b,c)r,d)q)p => ((a,b)p,(c,d)q)r */ \
+	static inline __type *kavl_rotate2_##suf(__type *p, int dir) { \
+		int b1, opp = 1 - dir; \
+		__type *q = p->__head.p[opp], *r = q->__head.p[dir]; \
+		unsigned size_x_dir = kavl_size_child(__head, r, dir); \
+		r->__head.size = p->__head.size; \
+		p->__head.size -= q->__head.size - size_x_dir; \
+		q->__head.size -= size_x_dir + 1; \
+		p->__head.p[opp] = r->__head.p[dir]; \
+		r->__head.p[dir] = p; \
+		q->__head.p[dir] = r->__head.p[opp]; \
+		r->__head.p[opp] = q; \
+		b1 = dir == 0? +1 : -1; \
+		if (r->__head.balance == b1) q->__head.balance = 0, p->__head.balance = -b1; \
+		else if (r->__head.balance == 0) q->__head.balance = p->__head.balance = 0; \
+		else q->__head.balance = b1, p->__head.balance = 0; \
+		r->__head.balance = 0; \
+		return r; \
+	}
+
+#define __KAVL_INSERT(suf, __scope, __type, __head, __cmp) \
+	__scope __type *kavl_insert_##suf(__type **root_, __type *x, unsigned *cnt_) { \
+		unsigned char stack[KAVL_MAX_DEPTH]; \
+		__type *path[KAVL_MAX_DEPTH]; \
+		__type *bp, *bq; \
+		__type *p, *q, *r = 0; /* _r_ is potentially the new root */ \
+		int i, which = 0, top, b1, path_len; \
+		unsigned cnt = 0; \
+		bp = *root_, bq = 0; \
+		/* find the insertion location */ \
+		for (p = bp, q = bq, top = path_len = 0; p; q = p, p = p->__head.p[which]) { \
+			int cmp; \
+			cmp = __cmp(x, p); \
+			if (cmp >= 0) cnt += kavl_size_child(__head, p, 0) + 1; \
+			if (cmp == 0) { \
+				if (cnt_) *cnt_ = cnt; \
+				return p; \
+			} \
+			if (p->__head.balance != 0) \
+				bq = q, bp = p, top = 0; \
+			stack[top++] = which = (cmp > 0); \
+			path[path_len++] = p; \
+		} \
+		if (cnt_) *cnt_ = cnt; \
+		x->__head.balance = 0, x->__head.size = 1, x->__head.p[0] = x->__head.p[1] = 0; \
+		if (q == 0) *root_ = x; \
+		else q->__head.p[which] = x; \
+		if (bp == 0) return x; \
+		for (i = 0; i < path_len; ++i) ++path[i]->__head.size; \
+		for (p = bp, top = 0; p != x; p = p->__head.p[stack[top]], ++top) /* update balance factors */ \
+			if (stack[top] == 0) --p->__head.balance; \
+			else ++p->__head.balance; \
+		if (bp->__head.balance > -2 && bp->__head.balance < 2) return x; /* no re-balance needed */ \
+		/* re-balance */ \
+		which = (bp->__head.balance < 0); \
+		b1 = which == 0? +1 : -1; \
+		q = bp->__head.p[1 - which]; \
+		if (q->__head.balance == b1) { \
+			r = kavl_rotate1_##suf(bp, which); \
+			q->__head.balance = bp->__head.balance = 0; \
+		} else r = kavl_rotate2_##suf(bp, which); \
+		if (bq == 0) *root_ = r; \
+		else bq->__head.p[bp != bq->__head.p[0]] = r; \
+		return x; \
+	}
+
+#define __KAVL_ERASE(suf, __scope, __type, __head, __cmp) \
+	__scope __type *kavl_erase_##suf(__type **root_, const __type *x, unsigned *cnt_) { \
+		__type *p, *path[KAVL_MAX_DEPTH], fake; \
+		unsigned char dir[KAVL_MAX_DEPTH]; \
+		int i, d = 0, cmp; \
+		unsigned cnt = 0; \
+		fake.__head.p[0] = *root_, fake.__head.p[1] = 0; \
+		if (cnt_) *cnt_ = 0; \
+		if (x) { \
+			for (cmp = -1, p = &fake; cmp; cmp = __cmp(x, p)) { \
+				int which = (cmp > 0); \
+				if (cmp > 0) cnt += kavl_size_child(__head, p, 0) + 1; \
+				dir[d] = which; \
+				path[d++] = p; \
+				p = p->__head.p[which]; \
+				if (p == 0) { \
+					if (cnt_) *cnt_ = 0; \
+					return 0; \
+				} \
+			} \
+			cnt += kavl_size_child(__head, p, 0) + 1; /* because p==x is not counted */ \
+		} else { \
+			for (p = &fake, cnt = 1; p; p = p->__head.p[0]) \
+				dir[d] = 0, path[d++] = p; \
+			p = path[--d]; \
+		} \
+		if (cnt_) *cnt_ = cnt; \
+		for (i = 1; i < d; ++i) --path[i]->__head.size; \
+		if (p->__head.p[1] == 0) { /* ((1,.)2,3)4 => (1,3)4; p=2 */ \
+			path[d-1]->__head.p[dir[d-1]] = p->__head.p[0]; \
+		} else { \
+			__type *q = p->__head.p[1]; \
+			if (q->__head.p[0] == 0) { /* ((1,2)3,4)5 => ((1)2,4)5; p=3 */ \
+				q->__head.p[0] = p->__head.p[0]; \
+				q->__head.balance = p->__head.balance; \
+				path[d-1]->__head.p[dir[d-1]] = q; \
+				path[d] = q, dir[d++] = 1; \
+				q->__head.size = p->__head.size - 1; \
+			} else { /* ((1,((.,2)3,4)5)6,7)8 => ((1,(2,4)5)3,7)8; p=6 */ \
+				__type *r; \
+				int e = d++; /* backup _d_ */\
+				for (;;) { \
+					dir[d] = 0; \
+					path[d++] = q; \
+					r = q->__head.p[0]; \
+					if (r->__head.p[0] == 0) break; \
+					q = r; \
+				} \
+				r->__head.p[0] = p->__head.p[0]; \
+				q->__head.p[0] = r->__head.p[1]; \
+				r->__head.p[1] = p->__head.p[1]; \
+				r->__head.balance = p->__head.balance; \
+				path[e-1]->__head.p[dir[e-1]] = r; \
+				path[e] = r, dir[e] = 1; \
+				for (i = e + 1; i < d; ++i) --path[i]->__head.size; \
+				r->__head.size = p->__head.size - 1; \
+			} \
+		} \
+		while (--d > 0) { \
+			__type *q = path[d]; \
+			int which, other, b1 = 1, b2 = 2; \
+			which = dir[d], other = 1 - which; \
+			if (which) b1 = -b1, b2 = -b2; \
+			q->__head.balance += b1; \
+			if (q->__head.balance == b1) break; \
+			else if (q->__head.balance == b2) { \
+				__type *r = q->__head.p[other]; \
+				if (r->__head.balance == -b1) { \
+					path[d-1]->__head.p[dir[d-1]] = kavl_rotate2_##suf(q, which); \
+				} else { \
+					path[d-1]->__head.p[dir[d-1]] = kavl_rotate1_##suf(q, which); \
+					if (r->__head.balance == 0) { \
+						r->__head.balance = -b1; \
+						q->__head.balance = b1; \
+						break; \
+					} else r->__head.balance = q->__head.balance = 0; \
+				} \
+			} \
+		} \
+		*root_ = fake.__head.p[0]; \
+		return p; \
+	}
+
+#define kavl_free(__type, __head, __root, __free) do { \
+		__type *_p, *_q; \
+		for (_p = __root; _p; _p = _q) { \
+			if (_p->__head.p[0] == 0) { \
+				_q = _p->__head.p[1]; \
+				__free(_p); \
+			} else { \
+				_q = _p->__head.p[0]; \
+				_p->__head.p[0] = _q->__head.p[1]; \
+				_q->__head.p[1] = _p; \
+			} \
+		} \
+	} while (0)
+
+#define __KAVL_ITR(suf, __scope, __type, __head, __cmp) \
+	struct kavl_itr_##suf { \
+		const __type *stack[KAVL_MAX_DEPTH], **top, *right; /* _right_ points to the right child of *top */ \
+	}; \
+	__scope void kavl_itr_first_##suf(const __type *root, struct kavl_itr_##suf *itr) { \
+		const __type *p; \
+		for (itr->top = itr->stack - 1, p = root; p; p = p->__head.p[0]) \
+			*++itr->top = p; \
+		itr->right = (*itr->top)->__head.p[1]; \
+	} \
+	__scope int kavl_itr_find_##suf(const __type *root, const __type *x, struct kavl_itr_##suf *itr) { \
+		const __type *p = root; \
+		itr->top = itr->stack - 1; \
+		while (p != 0) { \
+			int cmp; \
+			cmp = __cmp(x, p); \
+			if (cmp < 0) *++itr->top = p, p = p->__head.p[0]; \
+			else if (cmp > 0) p = p->__head.p[1]; \
+			else break; \
+		} \
+		if (p) { \
+			*++itr->top = p; \
+			itr->right = p->__head.p[1]; \
+			return 1; \
+		} else if (itr->top >= itr->stack) { \
+			itr->right = (*itr->top)->__head.p[1]; \
+			return 0; \
+		} else return 0; \
+	} \
+	__scope int kavl_itr_next_##suf(struct kavl_itr_##suf *itr) { \
+		for (;;) { \
+			const __type *p; \
+			for (p = itr->right, --itr->top; p; p = p->__head.p[0]) \
+				*++itr->top = p; \
+			if (itr->top < itr->stack) return 0; \
+			itr->right = (*itr->top)->__head.p[1]; \
+			return 1; \
+		} \
+	}
+
+/**
+ * Insert a node to the tree
+ *
+ * @param suf     name suffix used in KAVL_INIT()
+ * @param proot   pointer to the root of the tree (in/out: root may change)
+ * @param x       node to insert (in)
+ * @param cnt     number of nodes smaller than or equal to _x_; can be NULL (out)
+ *
+ * @return _x_ if not present in the tree, or the node equal to x.
+ */
+#define kavl_insert(suf, proot, x, cnt) kavl_insert_##suf(proot, x, cnt)
+
+/**
+ * Find a node in the tree
+ *
+ * @param suf     name suffix used in KAVL_INIT()
+ * @param root    root of the tree
+ * @param x       node value to find (in)
+ * @param cnt     number of nodes smaller than or equal to _x_; can be NULL (out)
+ *
+ * @return node equal to _x_ if present, or NULL if absent
+ */
+#define kavl_find(suf, root, x, cnt) kavl_find_##suf(root, x, cnt)
+
+/**
+ * Delete a node from the tree
+ *
+ * @param suf     name suffix used in KAVL_INIT()
+ * @param proot   pointer to the root of the tree (in/out: root may change)
+ * @param x       node value to delete; if NULL, delete the first node (in)
+ *
+ * @return node removed from the tree if present, or NULL if absent
+ */
+#define kavl_erase(suf, proot, x, cnt) kavl_erase_##suf(proot, x, cnt)
+#define kavl_erase_first(suf, proot) kavl_erase_##suf(proot, 0, 0)
+
+#define kavl_itr_t(suf) struct kavl_itr_##suf
+
+/**
+ * Place the iterator at the smallest object
+ *
+ * @param suf     name suffix used in KAVL_INIT()
+ * @param root    root of the tree
+ * @param itr     iterator
+ */
+#define kavl_itr_first(suf, root, itr) kavl_itr_first_##suf(root, itr)
+
+/**
+ * Place the iterator at the object equal to or greater than the query
+ *
+ * @param suf     name suffix used in KAVL_INIT()
+ * @param root    root of the tree
+ * @param x       query (in)
+ * @param itr     iterator (out)
+ *
+ * @return 1 if find; 0 otherwise. kavl_at(itr) is NULL if and only if query is
+ *         larger than all objects in the tree
+ */
+#define kavl_itr_find(suf, root, x, itr) kavl_itr_find_##suf(root, x, itr)
+
+/**
+ * Move to the next object in order
+ *
+ * @param itr     iterator (modified)
+ *
+ * @return 1 if there is a next object; 0 otherwise
+ */
+#define kavl_itr_next(suf, itr) kavl_itr_next_##suf(itr)
+
+/**
+ * Return the pointer at the iterator
+ *
+ * @param itr     iterator
+ *
+ * @return pointer if present; NULL otherwise
+ */
+#define kavl_at(itr) ((itr)->top < (itr)->stack? 0 : *(itr)->top)
+
+#define KAVL_INIT2(suf, __scope, __type, __head, __cmp) \
+	__KAVL_FIND(suf, __scope, __type, __head,  __cmp) \
+	__KAVL_ROTATE(suf, __type, __head) \
+	__KAVL_INSERT(suf, __scope, __type, __head, __cmp) \
+	__KAVL_ERASE(suf, __scope, __type, __head, __cmp) \
+	__KAVL_ITR(suf, __scope, __type, __head, __cmp)
+
+#define KAVL_INIT(suf, __type, __head, __cmp) \
+	KAVL_INIT2(suf,, __type, __head, __cmp)
+
+#endif