Pit Lib Tablestuff

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Tables Library code

[!] VersionNotice: The below code pertains to an older Lua version, Lua 4. It does not run as is under Lua 5.

-- Lua 4



-- table stuff: find a value in a table

function tfind(t, s)

 return foreachi(t, function(i, v) if v==%s then return i end end)

end



-- like tinsert for sets: only adds if not already in the table

function tadd(t, v) 

 if not tfind(t, v) then tinsert(t, v) end

end



-- print entire table, good for debugging

function tdump(table)

 if type(table) ~= "table" then

  print(table) -- dump is the same as print on non-table values

 else

  local indizes = {}

  foreach(table, function(i,v) tinsert(%indizes, i) end)

  if getn(indizes) == 0 then

   print("<empty table>")

  else

   sort(indizes)

   foreachi(indizes, function(_, index)

    local value = %table[index]

    if type(index) == "string" then

     print(index .. ":\t" .. tostring(value))

    else

     print("[" .. index .. "]\t" .. tostring(value))

    end

   end)

  end

 end

end



-- makes a deep copy of a given table (the 2nd param is optional and for internal use)

-- circular dependencies are correctly copied.

function tcopy(t, lookup_table)

 local copy = {}

 for i,v in t do

  if type(v) ~= "table" then

   copy[i] = v

  else

   lookup_table = lookup_table or {}

   lookup_table[t] = copy

   if lookup_table[v] then

    copy[i] = lookup_table[v] -- we already copied this table. reuse the copy.

   else

    copy[i] = tcopy(v,lookup_table) -- not yet copied. copy it.

   end

  end

 end

 return copy

end

Examples:

t = {1,2,3,{"a","b"}}

if tfind(t,3) then 

        tadd(t,4) -- adds a 5th value

        tadd(t,1) -- doesn't add again

        tadd(t,t) -- adds a 6th value: circular reference to self

end

t2 = tcopy(t) -- make a deep copy of t.

print(t2)

print(t2[6]) -- see? t2[6] points to t2, as expected

tdump(t2)

Comments

not-necessarily-directed-at-PetersStdLib rants:

• Lua's tinsert and tremove are badly named, as they are list operations as opposed to table operations
• the Lua library function naming style (runningwordstogetherlikethis) is not scalable and should not be imitated!

VersionNotice: tinsert and tremove are Lua4 functions, which are table.insert and table.remove in Lua 5.

I somewhat have to agree on that, but I wanted to seamlessly extend the standard libraries of lua. Perhaps it would be a better idea to completely replace the standardlibrary with a better named one, but I guess this would scare away possible users. Maybe the Lua authors will address this issue in a future version of Lua? (together with the "n-field" issue in tables) --PeterPrade

VersionNotice: The n-field issue is fixed in Lua 5. See LuaTableSize.

See Also

• TableSerialization - Recursive table print/serialization