finish PIVector doc

main.cpp

@@ -62,8 +62,10 @@ PICout operator <<(PICout s, const ConstChars & v) {
 }
 
 int main(int argc, char * argv[]) {
-	PIVector<int> v{1, 2, 3, 4};
-	PIVector<PIVector<int>> v2 = v.reshape(2,2, ReshapeByRow);
-	piCout << v2;
+	PIVector<int> v{1, 2, 3, 4, 5, 6};
+	PIVector<PIVector<int>> xv = v.reshape(3,2);
+	piCout << xv;
+	piCout << xv.flatten<int>();
+	piCout << xv.reshape<int>(2,3);
 	return 0;
 }