Add parser

Author: antonmedv

node.go

@@ -0,0 +1,72 @@
+package expr
+
+// Node items of abstract syntax tree.
+type Node interface{}
+
+type nilNode struct{}
+
+type identifierNode struct {
+	value string
+}
+
+type numberNode struct {
+	value float64
+}
+
+type boolNode struct {
+	value bool
+}
+
+type textNode struct {
+	value string
+}
+
+type nameNode struct {
+	name string
+}
+
+type unaryNode struct {
+	operator string
+	node     Node
+}
+
+type binaryNode struct {
+	operator string
+	left     Node
+	right    Node
+}
+
+type propertyNode struct {
+	node     Node
+	property Node
+}
+
+type methodNode struct {
+	node      Node
+	property  identifierNode
+	arguments []Node
+}
+
+type functionNode struct {
+	name      string
+	arguments []Node
+}
+
+type conditionalNode struct {
+	cond Node
+	exp1 Node
+	exp2 Node
+}
+
+type arrayNode struct {
+	nodes []Node
+}
+
+type mapNode struct {
+	pairs []pairNode
+}
+
+type pairNode struct {
+	key   Node
+	value Node
+}