Fix inconsistency with add operator, Added switch/case, Added default pipeline, Filter block with format function (take 3)

.gitignore

@@ -1,2 +1,2 @@
 .DS_Store
-.idea
+.idea

constructors.go

@@ -86,6 +86,10 @@ func (t *Template) newNil(pos Pos) *NilNode {
 	return &NilNode{NodeBase: NodeBase{TemplateName: t.Name, NodeType: NodeNil, Pos: pos}}
 }
 
+func (t *Template) newUndefined(pos Pos) *UndefinedNode {
+	return &UndefinedNode{NodeBase: NodeBase{TemplateName: t.Name, NodeType: NodeUndefined, Pos: pos}}
+}
+
 func (t *Template) newField(pos Pos, ident string) *FieldNode {
 	return &FieldNode{NodeBase: NodeBase{TemplateName: t.Name, NodeType: NodeField, Pos: pos}, Ident: strings.Split(ident[1:], ".")} //[1:] to drop leading period
 }
@@ -114,6 +118,18 @@ func (t *Template) newElse(pos Pos, line int) *elseNode {
 	return &elseNode{NodeBase: NodeBase{TemplateName: t.Name, NodeType: nodeElse, Pos: pos, Line: line}}
 }
 
+func (t *Template) newFilter(pos Pos, line int, set *SetNode, pipe Expression, list, elseList *ListNode) *FilterNode {
+	return &FilterNode{BranchNode{NodeBase: NodeBase{TemplateName: t.Name, NodeType: NodeFilter, Pos: pos, Line: line}, Set: set, Expression: pipe, List: list, ElseList: elseList}}
+}
+
+func (t *Template) newCase(pos Pos, line int, pipe Expression, list *ListNode) *CaseNode {
+	return &CaseNode{BranchNode{NodeBase: NodeBase{TemplateName: t.Name, NodeType: NodeCase, Pos: pos, Line: line}, Expression: pipe, List: list}}
+}
+
+func (t *Template) newSwitch(pos Pos, line int, set *SetNode, pipe Expression, list, elseList *ListNode) *SwitchNode {
+	return &SwitchNode{BranchNode{NodeBase: NodeBase{TemplateName: t.Name, NodeType: NodeSwitch, Pos: pos, Line: line}, Set: set, Expression: pipe, List: list, ElseList: elseList}}
+}
+
 func (t *Template) newIf(pos Pos, line int, set *SetNode, pipe Expression, list, elseList *ListNode) *IfNode {
 	return &IfNode{BranchNode{NodeBase: NodeBase{TemplateName: t.Name, NodeType: NodeIf, Pos: pos, Line: line}, Set: set, Expression: pipe, List: list, ElseList: elseList}}
 }

default.go

@@ -52,6 +52,14 @@ func init() {
 		"unsafe":    reflect.ValueOf(SafeWriter(unsafePrinter)),
 		"writeJson": reflect.ValueOf(jsonRenderer),
 		"json":      reflect.ValueOf(json.Marshal),
+		"default": reflect.ValueOf(Func(func(a Arguments) reflect.Value {
+			a.RequireNumOfArguments("default", 1, -1)
+			return a.Get(0)
+		})),
+		"format": reflect.ValueOf(Func(func(a Arguments) reflect.Value {
+			a.RequireNumOfArguments("format", 1, -1)
+			return a.Get(0)
+		})),
 		"isset": reflect.ValueOf(Func(func(a Arguments) reflect.Value {
 			a.RequireNumOfArguments("isset", 1, -1)
 			for i := 0; i < len(a.argExpr); i++ {
@@ -76,7 +84,7 @@ func init() {
 				return reflect.ValueOf(expression.NumField())
 			}
 
-			a.Panicf("inválid value type %s in len builtin", expression.Type())
+			a.Panicf("invalid value type %s in len builtin", expression.Type())
 			return reflect.Value{}
 		})),
 		"includeIfExists": reflect.ValueOf(Func(func(a Arguments) reflect.Value {