using metatables for table generation, allowing “addition” of dictionaries

1 files changed, 44 insertions, 9 deletions

diff --git a/tex/context/third/transliterator/t-transliterator.mkiv b/tex/context/third/transliterator/t-transliterator.mkiv
index ef8c15e..b4a3c86 100644
--- a/tex/context/third/transliterator/t-transliterator.mkiv
+++ b/tex/context/third/transliterator/t-transliterator.mkiv
@@ -54,7 +54,7 @@ translit.debug_count = 0
 %D We want to keep track of all the tables we'll create so we put them into
 %D a separate dictionary accompanied by a description string.
 \startluacode
-translit.tables = {}
+translit.tables = translit.tables or {}
 \stopluacode
 
 
@@ -96,6 +96,35 @@ translit.ru_consonants = {"б", "в", "г", "д", "ж", "з", "к", "л", "м",
 %D and
 %D trans_tables_trsc.lua.}
 
+%D Metatables allow for easy concatenation.
+\startluacode
+
+do
+    -- This returns the Union of both key sets for the “+” operator.
+    -- The values of the first table will be updated (read: overridden) by those given in the second.
+    local Dict_add = {
+        __add = function (dict_a, dict_b)
+            assert (type(dict_a) == "table" and type(dict_b) == "table")
+            local dict_result = setmetatable({}, Dict_add)
+
+            for key, val in pairs(dict_a) do
+                dict_result[key] = val
+            end
+
+            for key, val in pairs(dict_b) do
+                dict_result[key] = val
+            end
+            return dict_result
+        end
+    }
+
+    function translit.make_add_dict(dict)
+        return setmetatable(dict, Dict_add)
+    end
+end
+
+\stopluacode
+
 %D The function \type{translit.subst(s, t)} is used to replace any key of
 %D \type{t} that occurs in \type{s} with the according value of \type{t}.
 
@@ -116,14 +145,20 @@ end
 \startluacode
 
 
-function translit.add_table (t, ...)
-  for _,tab in ipairs(arg) do
-    for key, value in pairs (tab) do
-      t[key] = value
-    end
-  end
-  return t
-end
+--function translit.add_table (...)
+  --print ("---------------HERE---------------")
+  --print (type(arg) .. ", Länge: " .. #arg)
+  --local t = translit.make_add_dict{}
+  --local cnt = 0
+  --for _, tab in pairs(arg) do
+    --cnt=cnt+1
+    --print(cnt .. " - " .. type(tab))
+    --t = t + tab
+  --end
+  --print(cnt)
+  --for i,j in pairs(t) do print (i,j) end
+  --return t
+--end
 
 \stopluacode
 %D We might want to have all the table data nicely formatted by \CONTEXT\