From 0ddc554ac0261e84f9dafb40067ba834cd4509fe Mon Sep 17 00:00:00 2001
From: Lars Mueller <appgurulars@gmx.de>
Date: Fri, 25 Dec 2020 17:54:36 +0100
Subject: [PATCH] Add table.is_circular

---
 table.lua | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/table.lua b/table.lua
index df30411..4ce7dff 100644
--- a/table.lua
+++ b/table.lua
@@ -39,6 +39,26 @@ function shuffle(table)
     return table
 end
 
+function is_circular(table)
+    assert(type(table) == "table")
+    local known = {}
+    local function _is_circular(value)
+        if type(value) ~= "table" then
+            return false
+        end
+        if known[value] then
+            return true
+        end
+        known[value] = true
+        for key, value in pairs(value) do
+            if _is_circular(key) or _is_circular(value) then
+                return true
+            end
+        end
+    end
+    return _is_circular(table)
+end
+
 function equals_noncircular(table_1, table_2)
     local is_equal = table_1 == table_2
     if is_equal or type(table_1) ~= "table" or type(table_2) ~= "table" then