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diff --git a/Data/Libraries/Penlight/lua/pl/OrderedMap.lua b/Data/Libraries/Penlight/lua/pl/OrderedMap.lua
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+++ b/Data/Libraries/Penlight/lua/pl/OrderedMap.lua
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+--- OrderedMap, a map which preserves ordering.
+--
+-- Derived from `pl.Map`.
+--
+-- Dependencies: `pl.utils`, `pl.tablex`, `pl.class`, `pl.List`, `pl.Map`
+-- @classmod pl.OrderedMap
+
+local tablex = require 'pl.tablex'
+local utils = require 'pl.utils'
+local List = require 'pl.List'
+local index_by,tsort,concat = tablex.index_by,table.sort,table.concat
+
+local class = require 'pl.class'
+local Map = require 'pl.Map'
+
+local OrderedMap = class(Map)
+OrderedMap._name = 'OrderedMap'
+
+local rawset = rawset
+
+--- construct an OrderedMap.
+-- Will throw an error if the argument is bad.
+-- @param t optional initialization table, same as for @{OrderedMap:update}
+function OrderedMap:_init (t)
+    rawset(self,'_keys',List())
+    if t then
+        local map,err = self:update(t)
+        if not map then error(err,2) end
+    end
+end
+
+local assert_arg,raise = utils.assert_arg,utils.raise
+
+--- update an OrderedMap using a table.
+-- If the table is itself an OrderedMap, then its entries will be appended.
+-- if it s a table of the form `{{key1=val1},{key2=val2},...}` these will be appended.
+--
+-- Otherwise, it is assumed to be a map-like table, and order of extra entries is arbitrary.
+-- @tab t a table.
+-- @return the map, or nil in case of error
+-- @return the error message
+function OrderedMap:update (t)
+    assert_arg(1,t,'table')
+    if OrderedMap:class_of(t) then
+       for k,v in t:iter() do
+           self:set(k,v)
+       end
+    elseif #t > 0 then -- an array must contain {key=val} tables
+       if type(t[1]) == 'table' then
+           for _,pair in ipairs(t) do
+               local key,value = next(pair)
+               if not key then return raise 'empty pair initialization table' end
+               self:set(key,value)
+           end
+       else
+           return raise 'cannot use an array to initialize an OrderedMap'
+       end
+    else
+       for k,v in pairs(t) do
+           self:set(k,v)
+       end
+    end
+   return self
+end
+
+--- set the key's value.   This key will be appended at the end of the map.
+--
+-- If the value is nil, then the key is removed.
+-- @param key the key
+-- @param val the value
+-- @return the map
+function OrderedMap:set (key,val)
+    if rawget(self, key) == nil and val ~= nil then -- new key
+        self._keys:append(key) -- we keep in order
+        rawset(self,key,val)  -- don't want to provoke __newindex!
+    else -- existing key-value pair
+        if val == nil then
+            self._keys:remove_value(key)
+            rawset(self,key,nil)
+        else
+            self[key] = val
+        end
+    end
+    return self
+end
+
+OrderedMap.__newindex = OrderedMap.set
+
+--- insert a key/value pair before a given position.
+-- Note: if the map already contains the key, then this effectively
+-- moves the item to the new position by first removing at the old position.
+-- Has no effect if the key does not exist and val is nil
+-- @int pos a position starting at 1
+-- @param key the key
+-- @param val the value; if nil use the old value
+function OrderedMap:insert (pos,key,val)
+    local oldval = self[key]
+    val = val or oldval
+    if oldval then
+        self._keys:remove_value(key)
+    end
+    if val then
+        self._keys:insert(pos,key)
+        rawset(self,key,val)
+    end
+    return self
+end
+
+--- return the keys in order.
+-- (Not a copy!)
+-- @return List
+function OrderedMap:keys ()
+    return self._keys
+end
+
+--- return the values in order.
+-- this is relatively expensive.
+-- @return List
+function OrderedMap:values ()
+    return List(index_by(self,self._keys))
+end
+
+--- sort the keys.
+-- @func cmp a comparison function as for @{table.sort}
+-- @return the map
+function OrderedMap:sort (cmp)
+    tsort(self._keys,cmp)
+    return self
+end
+
+--- iterate over key-value pairs in order.
+function OrderedMap:iter ()
+    local i = 0
+    local keys = self._keys
+    local idx
+    return function()
+        i = i + 1
+        if i > #keys then return nil end
+        idx = keys[i]
+        return idx,self[idx]
+    end
+end
+
+--- iterate over an ordered map (5.2).
+-- @within metamethods
+-- @function OrderedMap:__pairs
+OrderedMap.__pairs = OrderedMap.iter
+
+--- string representation of an ordered map.
+-- @within metamethods
+function OrderedMap:__tostring ()
+    local res = {}
+    for i,v in ipairs(self._keys) do
+        local val = self[v]
+        local vs = tostring(val)
+        if type(val) ~= 'number' then
+            vs = '"'..vs..'"'
+        end
+        res[i] = tostring(v)..'='..vs
+    end
+    return '{'..concat(res,',')..'}'
+end
+
+return OrderedMap
+
+
+