1 files changed, 84 insertions, 0 deletions
diff --git a/luaextra-set.lua b/luaextra-set.lua
new file mode 100644
index 0000000..f844d0b
--- /dev/null
+++ b/luaextra-set.lua
@@ -0,0 +1,84 @@
+if not modules then modules = { } end modules ['l-set'] = {
+    version   = 1.001,
+    comment   = "companion to luat-lib.mkiv",
+    author    = "Hans Hagen, PRAGMA-ADE, Hasselt NL",
+    copyright = "PRAGMA ADE / ConTeXt Development Team",
+    license   = "see context related readme files"
+}
+
+set = set or { }
+
+local nums   = { }
+local tabs   = { }
+local concat = table.concat
+local next, type = next, type
+
+set.create = table.tohash
+
+function set.tonumber(t)
+    if next(t) then
+        local s = ""
+    --  we could save mem by sorting, but it slows down
+        for k, v in next, t do
+            if v then
+            --  why bother about the leading space
+                s = s .. " " .. k
+            end
+        end
+        local n = nums[s]
+        if not n then
+            n = #tabs + 1
+            tabs[n] = t
+            nums[s] = n
+        end
+        return n
+    else
+        return 0
+    end
+end
+
+function set.totable(n)
+    if n == 0 then
+        return { }
+    else
+        return tabs[n] or { }
+    end
+end
+
+function set.tolist(n)
+    if n == 0 or not tabs[n] then
+        return ""
+    else
+        local t = { }
+        for k, v in next, tabs[n] do
+            if v then
+                t[#t+1] = k
+            end
+        end
+        return concat(t," ")
+    end
+end
+
+function set.contains(n,s)
+    if type(n) == "table" then
+        return n[s]
+    elseif n == 0 then
+        return false
+    else
+        local t = tabs[n]
+        return t and t[s]
+    end
+end
+
+--~ local c = set.create{'aap','noot','mies'}
+--~ local s = set.tonumber(c)
+--~ local t = set.totable(s)
+--~ print(t['aap'])
+--~ local c = set.create{'zus','wim','jet'}
+--~ local s = set.tonumber(c)
+--~ local t = set.totable(s)
+--~ print(t['aap'])
+--~ print(t['jet'])
+--~ print(set.contains(t,'jet'))
+--~ print(set.contains(t,'aap'))
+