The list operator '<<' (append) and '>>' (prepend) have been replaced

with the new operators '<+' and '+>' respectively.
'<<' and '>>' are now used only for left and right binary shit
respectively. Further, their priority has been increased moving them to
a higher priority than that of the assignment operator.

symbol-map.go

@@ -84,8 +84,8 @@ func init() {
 		SymQuestionExclam:  {"?!", symClassOperator},     //  49: '?!'
 		SymDoubleAt:        {"@@", symClassOperator},     //  50: '@@'
 		SymDoubleColon:     {"::", symClassOperator},     //  51: '::'
-		SymInsert:          {">>", symClassOperator},     //  52: '>>'
-		SymAppend:          {"<<", symClassOperator},     //  53: '<<'
+		SymDoubleGreater:   {">>", symClassOperator},     //  52: '>>'
+		SymDoubleLess:      {"<<", symClassOperator},     //  53: '<<'
 		SymCaret:           {"^", symClassOperator},      //  54: '^'
 		SymDollarRound:     {"$(", symClassOperator},     //  55: '$('
 		SymOpenClosedRound: {"()", symClassPostOp},       //  56: '()'
@@ -95,6 +95,8 @@ func init() {
 		SymStarEqual:       {"*=", symClassOperator},     //  60: '*='
 		SymSlashEqual:      {"/=", symClassOperator},     //  61: '/='
 		SymPercEqual:       {"%=", symClassOperator},     //  62: '%='
+		SymPlusGreater:     {"+>", symClassOperator},     //  63: '+>'
+		SymLessPlus:        {"<+", symClassOperator},     //  64: '<+'
 		// SymChangeSign
 		// SymUnchangeSign
 		// SymIdentifier