1 files changed, 49 insertions, 0 deletions
diff --git a/script/vm/node/union.lua b/script/vm/node/union.lua
new file mode 100644
index 00000000..a8c917d9
--- /dev/null
+++ b/script/vm/node/union.lua
@@ -0,0 +1,49 @@
+local state = require 'vm.state'
+
+---@class vm.node.union
+local mt = {}
+mt.__index = mt
+mt.type = 'union'
+
+---@param node   vm.node
+function mt:merge(node)
+    if not node then
+        return
+    end
+    if node.type == 'union' then
+        for _, c in ipairs(node) do
+            self[#self+1] = c
+        end
+    else
+        self[#self+1] = node
+    end
+end
+
+---@param source parser.object
+function mt:subscribeLiteral(source)
+    for _, c in ipairs(self) do
+        state.subscribeLiteral(source, c)
+        if c.type == 'cross' then
+            c:subscribeLiteral(source)
+        end
+    end
+end
+
+function mt:eachNode()
+    local i = 0
+    return function ()
+        i = i + 1
+        return self[i]
+    end
+end
+
+---@param me   parser.object
+---@param node vm.node
+---@return vm.node.union
+return function (me, node)
+    local union = setmetatable({
+        [1] = me,
+    }, mt)
+    union:merge(node)
+    return union
+end