readOr in reader macros

src/kiss/Helpers.hx

@@ -531,6 +531,7 @@ class Helpers {
         // plus macro-specific things.
         var interp = new KissInterp();
         interp.variables.set("read", Reader._assertRead.bind(_, k));
+        interp.variables.set("readOr", Reader._readOr.bind(_, k));
         interp.variables.set("readExpArray", Reader._readExpArray.bind(_, _, k));
         interp.variables.set("ReaderExp", ReaderExpDef);
         interp.variables.set("nextToken", Reader.nextToken.bind(_, "a token"));

src/kiss/Reader.hx

@@ -327,6 +327,15 @@ class Reader {
         }
     }
 
+    static function _readOr(stream:Stream, k:KissState, defaultExp:ReaderExp):ReaderExp {
+        return switch (_read(stream, k)) {
+            case Some(exp):
+                exp;
+            case None:
+                defaultExp;
+        }
+    }
+
     static var nestedReadExpArrayStartPositions = [];
     static var readExpArrayStartPositions = [];