+/** fac1 = "(" expr ")" */
+let fac1 = circumfix((x : TokenMatcheePair)=>
+thenDo(thenDo(thenDo(tk.toSome(x), tLParen), expr), tRParen), "fac1");
+
+let fac2 = tInt;
+
+let fac = orDo(fac1, fac2);
+
+
+
+/**
+ *
+ * term1 = fac (MUL | DIV) fac
+ */
+
+let term1 = midfix((x : TokenMatcheePair)=>
+ thenDo(thenDo(thenDo(tk.toSome(x), fac), orDo(tMul,tDiv)), fac), "term1");
+