diff --git a/playground/test.R b/playground/test.R
index 7c31428..bb37ec0 100644
--- a/playground/test.R
+++ b/playground/test.R
@@ -153,6 +153,67 @@ sumCalTest2 |>
 #   };
 # };
 
+# the following two results are equal
+system('currycarbon "((A,3000,20)+(B,2900,200)+(C,2800,70))+(((D,3500,60)+(E,3400,60))+(F,3300,30))" --densityFile /tmp/currycarbonSumCalTest1.tsv')
+
+sumCalTest1 <- readr::read_tsv(
+  "/tmp/currycarbonSumCalTest2.tsv",
+  col_types = readr::cols()
+)
+
+system('currycarbon "(A,3000,20)+(B,2900,200)+(C,2800,70)+(D,3500,60)+(E,3400,60)+(F,3300,30)" --densityFile /tmp/currycarbonSumCalTest2.tsv')
+
+sumCalTest2 <- readr::read_tsv(
+  "/tmp/currycarbonSumCalTest2.tsv",
+  col_types = readr::cols()
+)
+
+ggplot() +
+  geom_line(
+    data = sumCalTest2,
+    mapping = aes(x = yearBCAD, y = density),
+    color = "red"
+  ) +
+  geom_line(
+    data = sumCalTest2,
+    mapping = aes(x = yearBCAD, y = density),
+    color = "blue"
+  )
+
+# but the following two oxcal scripts are not - only the second one is similar to the currycarbon result
+# I think that's how it should be (2023-12-01)
+
+# Oxcal:
+#
+# Sum("(A+B+C)+((D*E)+F)")
+# {
+#   Sum("A+B+C")
+#   {
+#     R_Date("A",3000,20);
+#     R_Date("B",2900,200);
+#     R_Date("C",2800,70);
+#   };
+#   Sum("(D*E)+F")
+#   {
+#     Sum("D*E")
+#     {
+#       R_Date("D",3500,60);
+#       R_Date("E",3400,60);
+#     };
+#     R_Date("F",3300,30);
+#   };
+# };
+
+# Sum("(A+B+C)+((D*E)+F)")
+# {
+#   R_Date("A",3000,20);
+#   R_Date("B",2900,200);
+#   R_Date("C",2800,70);
+#   R_Date("D",3500,60);
+#   R_Date("E",3400,60);
+#   R_Date("F",3300,30);
+# };
+
 #### another test of the random age sampling ####
 
 system('currycarbon "A,3000,30+B,3200,40*C,3300,30" --samplesFile /tmp/currySamples.tsv -n 10000')