add Is...() and tests

query.go

@@ -1,25 +1,60 @@
 package goquery
 
 import (
+	"code.google.com/p/cascadia"
 	"exp/html"
 	"regexp"
 	"strings"
 )
 
+var rxNeedsContext = `^[\x20\t\r\n\f]*[>+~]|:(nth|eq|gt|lt|first|last|even|odd)(?:\((\d*)\)|)(?:[^-]|$)`
+
+// Is() checks the current matched set of elements against a selector and
+// returns true if at least one of these elements matches.
 func (this *Selection) Is(selector string) bool {
+	if len(this.Nodes) > 0 {
+		// The selector must be done on the document if it has positional criteria
+		if ok, e := regexp.MatchString(rxNeedsContext, selector); ok {
+			sel := this.document.Find(selector)
+			for _, n := range this.Nodes {
+				if sel.IndexOfNode(n) > -1 {
+					return true
+				}
+			}
 
+		} else if e != nil {
+			panic(e.Error())
+
+		} else {
+			// Attempt a match with the selector
+			cs := cascadia.MustCompile(selector)
+			if len(this.Nodes) == 1 {
+				return cs.Match(this.Nodes[0])
+			} else {
+				return len(cs.Filter(this.Nodes)) > 0
+			}
+		}
+	}
+
+	return false
 }
 
-func (this *Selection) IsFunction(func(int, *Selection) bool) bool {
-
+// Is() checks the current matched set of elements against a predicate and
+// returns true if at least one of these elements matches.
+func (this *Selection) IsFunction(f func(int, *Selection) bool) bool {
+	return this.FilterFunction(f).Length() > 0
 }
 
+// Is() checks the current matched set of elements against a Selection object
+// and returns true if at least one of these elements matches.
 func (this *Selection) IsSelection(s *Selection) bool {
-
+	return this.FilterSelection(s).Length() > 0
 }
 
+// Is() checks the current matched set of elements against the specified nodes
+// and returns true if at least one of these elements matches.
 func (this *Selection) IsNodes(nodes ...*html.Node) bool {
-
+	return this.FilterNodes(nodes...).Length() > 0
 }
 
 // HasClass() determines whether any of the matched elements are assigned the

query_test.go

@@ -4,6 +4,64 @@ import (
 	"testing"
 )
 
+func TestIs(t *testing.T) {
+	sel := Doc().Find(".footer p:nth-child(1)")
+	if !sel.Is("p") {
+		t.Error("Expected .footer p:nth-child(1) to be p.")
+	}
+}
+
+func TestIsPositional(t *testing.T) {
+	sel := Doc().Find(".footer p:nth-child(2)")
+	if !sel.Is("p:nth-child(2)") {
+		t.Error("Expected .footer p:nth-child(2) to be p:nth-child(2).")
+	}
+}
+
+func TestIsPositionalNot(t *testing.T) {
+	sel := Doc().Find(".footer p:nth-child(1)")
+	if sel.Is("p:nth-child(2)") {
+		t.Error("Expected .footer p:nth-child(1) NOT to be p:nth-child(2).")
+	}
+}
+
+func TestIsFunction(t *testing.T) {
+	ok := Doc().Find("div").IsFunction(func(i int, s *Selection) bool {
+		return s.HasClass("container-fluid")
+	})
+
+	if !ok {
+		t.Error("Expected some div to have a container-fluid class.")
+	}
+}
+
+func TestIsSelection(t *testing.T) {
+	sel := Doc().Find("div")
+	sel2 := Doc().Find(".pvk-gutter")
+
+	if !sel.IsSelection(sel2) {
+		t.Error("Expected some div to have a pvk-gutter class.")
+	}
+}
+
+func TestIsSelectionNot(t *testing.T) {
+	sel := Doc().Find("div")
+	sel2 := Doc().Find("a")
+
+	if sel.IsSelection(sel2) {
+		t.Error("Expected some div NOT to be an anchor.")
+	}
+}
+
+func TestIsNodes(t *testing.T) {
+	sel := Doc().Find("div")
+	sel2 := Doc().Find(".footer")
+
+	if !sel.IsNodes(sel2.Nodes[0]) {
+		t.Error("Expected some div to have a footer class.")
+	}
+}
+
 func TestHasClass(t *testing.T) {
 	sel := Doc().Find("div")
 	if !sel.HasClass("span12") {