diff --git a/compiler.go b/compiler.go
index 3b79c95..e8aaf64 100644
--- a/compiler.go
+++ b/compiler.go
@@ -215,6 +215,10 @@ func convertMatchers(matchers []match.Matcher, result []match.Matcher) []match.M
 }
 
 func compileMatchers(matchers []match.Matcher) (match.Matcher, error) {
+	if len(matchers) == 0 {
+		return nil, fmt.Errorf("compile error: need at least one matcher")
+	}
+
 	if m := glueMatchers(matchers); m != nil {
 		return m, nil
 	}
@@ -233,9 +237,8 @@ func compileMatchers(matchers []match.Matcher) (match.Matcher, error) {
 		}
 	}
 
-	if val == nil {
-		return nil, fmt.Errorf("could not convert matchers %s: need at least one matcher", match.Matchers(matchers))
-	}
+	//	_, ok := val.(match.BTree)
+	//	fmt.Println("a tree", ok)
 
 	left := matchers[:idx]
 	var right []match.Matcher
diff --git a/glob_test.go b/glob_test.go
index df8e0ab..6233f08 100644
--- a/glob_test.go
+++ b/glob_test.go
@@ -1,7 +1,10 @@
 package glob
 
 import (
+	"bytes"
+	"fmt"
 	"github.com/gobwas/glob/match"
+	"math/rand"
 	"reflect"
 	"testing"
 )
@@ -35,6 +38,43 @@ func glob(s bool, p, m string, d ...string) test {
 	return test{p, m, s, d}
 }
 
+func draw(pattern string, m match.Matcher) string {
+	if tree, ok := m.(match.BTree); ok {
+		return fmt.Sprintf(`digraph G {graph[label="%s"];%s}`, pattern, graphviz(tree, fmt.Sprintf("%x", rand.Int63())))
+	}
+
+	return m.String()
+}
+
+func graphviz(tree match.BTree, id string) string {
+	buf := &bytes.Buffer{}
+
+	fmt.Fprintf(buf, `"%s"[label="%s"];`, id, tree.Value.String())
+	for _, m := range []match.Matcher{tree.Left, tree.Right} {
+		switch n := m.(type) {
+		case nil:
+			rnd := rand.Int63()
+			fmt.Fprintf(buf, `"%x"[label="<nil>"];`, rnd)
+			//			fmt.Fprintf(buf, `"%s"->"%x"[label="len = 0"];`, id, rnd)
+			fmt.Fprintf(buf, `"%s"->"%x";`, id, rnd)
+
+		case match.BTree:
+			sub := fmt.Sprintf("%x", rand.Int63())
+			//			fmt.Fprintf(buf, `"%s"->"%s"[label="len=%d"];`, id, sub, n.Len())
+			fmt.Fprintf(buf, `"%s"->"%s";`, id, sub)
+			fmt.Fprintf(buf, graphviz(n, sub))
+
+		default:
+			rnd := rand.Int63()
+			fmt.Fprintf(buf, `"%x"[label="%s"];`, rnd, m.String())
+			//			fmt.Fprintf(buf, `"%s"->"%x"[label="len = %d"];`, id, rnd, m.Len())
+			fmt.Fprintf(buf, `"%s"->"%x";`, id, rnd)
+		}
+	}
+
+	return buf.String()
+}
+
 func TestCompilePattern(t *testing.T) {
 	for id, test := range []struct {
 		pattern string
@@ -42,7 +82,11 @@ func TestCompilePattern(t *testing.T) {
 		exp     match.Matcher
 	}{
 		{
-			pattern: "a?*",
+			pattern: "left*??B*abcd*[!b]??*abc*right",
+			exp:     match.Raw{"t"},
+		},
+		{
+			pattern: "abc*??def",
 			exp:     match.Raw{"t"},
 		},
 	} {
@@ -53,9 +97,8 @@ func TestCompilePattern(t *testing.T) {
 		}
 
 		matcher := glob.(match.Matcher)
-
 		if !reflect.DeepEqual(test.exp, matcher) {
-			t.Errorf("#%d unexpected compilation:\nexp: %s\nact: %s", id, test.exp, matcher)
+			t.Errorf("#%d unexpected compilation:\nexp: %s\nact: %s", id, test.exp, draw(test.pattern, matcher))
 			continue
 		}
 	}
diff --git a/match/any.go b/match/any.go
index 92c6274..f554b6a 100644
--- a/match/any.go
+++ b/match/any.go
@@ -44,5 +44,5 @@ func (self Any) Kind() Kind {
 }
 
 func (self Any) String() string {
-	return fmt.Sprintf("[any:%s]", self.Separators)
+	return fmt.Sprintf("<any:![%s]>", self.Separators)
 }
diff --git a/match/any_of.go b/match/any_of.go
index 605a771..46a6f36 100644
--- a/match/any_of.go
+++ b/match/any_of.go
@@ -84,5 +84,5 @@ func (self AnyOf) Kind() Kind {
 }
 
 func (self AnyOf) String() string {
-	return fmt.Sprintf("[any_of:%s]", self.Matchers)
+	return fmt.Sprintf("<any_of:[%s]>", self.Matchers)
 }
diff --git a/match/btree.go b/match/btree.go
index efa6ebc..9c3534d 100644
--- a/match/btree.go
+++ b/match/btree.go
@@ -112,23 +112,6 @@ func (self BTree) Match(s string) bool {
 	return false
 }
 
-const tpl = `
-"%p"[label="%s"]
-"%p"[label="%s"]
-"%p"[label="%s"]
-"%p"->"%p"
-"%p"->"%p"
-`
-
 func (self BTree) String() string {
-	//	return fmt.Sprintf("[btree:%s<-%s->%s]", self.Left, self.Value, self.Right)
-
-	l, r := "nil", "nil"
-	if self.Left != nil {
-		l = self.Left.String()
-	}
-	if self.Right != nil {
-		r = self.Right.String()
-	}
-	return fmt.Sprintf(tpl, &self, self.Value, &l, l, &r, r, &self, &l, &self, &r)
+	return fmt.Sprintf("<btree:[%s<-%s->%s]>", self.Left, self.Value, self.Right)
 }
diff --git a/match/contains.go b/match/contains.go
index 329dc3b..d7b2154 100644
--- a/match/contains.go
+++ b/match/contains.go
@@ -61,5 +61,9 @@ func (self Contains) Kind() Kind {
 }
 
 func (self Contains) String() string {
-	return fmt.Sprintf("[contains:needle=%s not=%t]", self.Needle, self.Not)
+	var not string
+	if self.Not {
+		not = "!"
+	}
+	return fmt.Sprintf("<contains:%s[%s]>", not, self.Needle)
 }
diff --git a/match/every_of.go b/match/every_of.go
index 36af182..4174ce3 100644
--- a/match/every_of.go
+++ b/match/every_of.go
@@ -79,5 +79,5 @@ func (self EveryOf) Kind() Kind {
 }
 
 func (self EveryOf) String() string {
-	return fmt.Sprintf("[every_of:%s]", self.Matchers)
+	return fmt.Sprintf("<every_of:[%s]>", self.Matchers)
 }
diff --git a/match/list.go b/match/list.go
index e83edd1..2ff1e1f 100644
--- a/match/list.go
+++ b/match/list.go
@@ -40,5 +40,10 @@ func (self List) Index(s string) (int, []int) {
 }
 
 func (self List) String() string {
-	return fmt.Sprintf("[list:list=%s not=%t]", self.List, self.Not)
+	var not string
+	if self.Not {
+		not = "!"
+	}
+
+	return fmt.Sprintf("<list:%s[%s]>", not, self.List)
 }
diff --git a/match/match.go b/match/match.go
index b22bc51..d16f9a9 100644
--- a/match/match.go
+++ b/match/match.go
@@ -42,7 +42,7 @@ func (m Matchers) String() string {
 		s = append(s, fmt.Sprint(matcher))
 	}
 
-	return fmt.Sprintf("matchers[%s]", strings.Join(s, ","))
+	return fmt.Sprintf("%s", strings.Join(s, ","))
 }
 
 func appendIfNotAsPrevious(target []int, val int) []int {
diff --git a/match/max.go b/match/max.go
index 58fffb6..67e5378 100644
--- a/match/max.go
+++ b/match/max.go
@@ -46,5 +46,5 @@ func (self Max) Kind() Kind {
 }
 
 func (self Max) String() string {
-	return fmt.Sprintf("[max:%d]", self.Limit)
+	return fmt.Sprintf("<max:%d>", self.Limit)
 }
diff --git a/match/min.go b/match/min.go
index 071ef88..5bba994 100644
--- a/match/min.go
+++ b/match/min.go
@@ -45,5 +45,5 @@ func (self Min) Kind() Kind {
 }
 
 func (self Min) String() string {
-	return fmt.Sprintf("[min:%d]", self.Limit)
+	return fmt.Sprintf("<min:%d>", self.Limit)
 }
diff --git a/match/prefix.go b/match/prefix.go
index 67b8856..49b22e6 100644
--- a/match/prefix.go
+++ b/match/prefix.go
@@ -54,5 +54,5 @@ func (self Prefix) Match(s string) bool {
 }
 
 func (self Prefix) String() string {
-	return fmt.Sprintf("[prefix:%s]", self.Prefix)
+	return fmt.Sprintf("<prefix:%s>", self.Prefix)
 }
diff --git a/match/prefix_suffix.go b/match/prefix_suffix.go
index e2a4838..9efffea 100644
--- a/match/prefix_suffix.go
+++ b/match/prefix_suffix.go
@@ -60,5 +60,5 @@ func (self PrefixSuffix) Match(s string) bool {
 }
 
 func (self PrefixSuffix) String() string {
-	return fmt.Sprintf("[prefix_suffix:%s-%s]", self.Prefix, self.Suffix)
+	return fmt.Sprintf("<prefix_suffix:[%s,%s]>", self.Prefix, self.Suffix)
 }
diff --git a/match/range.go b/match/range.go
index e709376..e771285 100644
--- a/match/range.go
+++ b/match/range.go
@@ -40,5 +40,9 @@ func (self Range) Index(s string) (int, []int) {
 }
 
 func (self Range) String() string {
-	return fmt.Sprintf("[range:%s-%s(%t)]", string(self.Lo), string(self.Hi), self.Not)
+	var not string
+	if self.Not {
+		not = "!"
+	}
+	return fmt.Sprintf("<range:%s[%s,%s]>", not, string(self.Lo), string(self.Hi))
 }
diff --git a/match/row.go b/match/row.go
index 46b4c90..2c337df 100644
--- a/match/row.go
+++ b/match/row.go
@@ -62,5 +62,5 @@ func (self Row) Kind() Kind {
 }
 
 func (self Row) String() string {
-	return fmt.Sprintf("[row:%s]", self.Matchers)
+	return fmt.Sprintf("<row:[%s]>", self.Matchers)
 }
diff --git a/match/single.go b/match/single.go
index f60d883..833f4c7 100644
--- a/match/single.go
+++ b/match/single.go
@@ -34,5 +34,5 @@ func (self Single) Kind() Kind {
 }
 
 func (self Single) String() string {
-	return fmt.Sprintf("[single:%s]", self.Separators)
+	return fmt.Sprintf("<single:![%s]>", self.Separators)
 }
diff --git a/match/suffix.go b/match/suffix.go
index 15266b7..c9e0425 100644
--- a/match/suffix.go
+++ b/match/suffix.go
@@ -39,5 +39,5 @@ func (self Suffix) Match(s string) bool {
 }
 
 func (self Suffix) String() string {
-	return fmt.Sprintf("[suffix:%s]", self.Suffix)
+	return fmt.Sprintf("<suffix:%s>", self.Suffix)
 }
diff --git a/match/super.go b/match/super.go
index f69bd8b..ad50d43 100644
--- a/match/super.go
+++ b/match/super.go
@@ -31,5 +31,5 @@ func (self Super) Kind() Kind {
 }
 
 func (self Super) String() string {
-	return fmt.Sprintf("[super]")
+	return fmt.Sprintf("<super>")
 }