1 files changed, 42 insertions, 0 deletions
diff --git a/src/document_tree/macro_util.rs b/src/document_tree/macro_util.rs
new file mode 100644
index 0000000..84e1b29
--- /dev/null
+++ b/src/document_tree/macro_util.rs
@@ -0,0 +1,42 @@
+macro_rules! cartesian_impl {
+    ($out:tt [] $b:tt $init_b:tt $submacro:tt) => {
+        $submacro!{$out}
+    };
+    ($out:tt [$a:tt, $($at:tt)*] [] $init_b:tt $submacro:tt) => {
+        cartesian_impl!{$out [$($at)*] $init_b $init_b $submacro}
+    };
+    ([$($out:tt)*] [$a:tt, $($at:tt)*] [$b:tt, $($bt:tt)*] $init_b:tt $submacro:tt) => {
+        cartesian_impl!{[$($out)* ($a, $b),] [$a, $($at)*] [$($bt)*] $init_b $submacro}
+    };
+}
+
+macro_rules! cartesian {
+    ( $submacro:tt, [$($a:tt)*], [$($b:tt)*]) => {
+        cartesian_impl!{[] [$($a)*,] [$($b)*,] [$($b)*,] $submacro}
+    };
+}
+
+
+#[cfg(test)]
+mod test {
+    macro_rules! print_cartesian {
+        ( [ $(($a1:tt, $a2:tt)),* , ] ) => {
+            fn test_f(x:i64, y:i64) -> Result<(i64, i64), ()> {
+                match (x, y) {
+                $(
+                    ($a1, $a2) => { Ok(($a1, $a2)) }
+                )*
+                _ => { Err(()) }
+                }
+            }
+        };
+    }
+
+    #[test]
+    fn test_print_cartesian() {
+        cartesian!(print_cartesian, [1, 2, 3], [4, 5, 6]);
+        assert_eq!(test_f(1, 4), Ok((1, 4)));
+        assert_eq!(test_f(1, 3), Err(()));
+        assert_eq!(test_f(3, 5), Ok((3, 5)));
+    }
+}