# Difference between revisions of "Module:TableTools"

--[[

-- TableTools -- -- -- -- This module includes a number of functions for dealing with Lua tables. -- -- It is a meta-module, meant to be called from other Lua modules, and should -- -- not be called directly from #invoke. --

--]]

local p = {}

-- Define often-used variables and functions. local floor = math.floor local infinity = math.huge

-- Define a unique value to represent NaN. This is because NaN cannot be used as a table key. local nan = {}

--[[

-- isPositiveInteger -- -- This function returns true if the given number is a positive integer, and false -- if not. Although it doesn't operate on tables, it is included here as it is -- useful for determining whether a given table key is in the array part or the -- hash part of a table.

--]] function p.isPositiveInteger(num) if type(num) == 'number' and num >= 1 and floor(num) == num and num < infinity then return true else return false end end

--[[

-- union -- -- This returns the union of the values of n tables, as an array. For example, for -- the tables {1, 3, 4, 5, foo = 7} and {2, bar = 3, 5, 6}, union will return -- {1, 2, 3, 4, 5, 6, 7}.

--]] function p.union(...) local vals, ret = {}, {} for i = 1, select('#', ...) do local t = select(i, ...) for k, v in pairs(t) do if type(v) == 'number' and tostring(v) == '-nan' then v = nan -- NaN cannot be a table key, so use a proxy variable. end vals[v] = true end end for val in pairs(vals) do if val == nan then -- This ensures that we output a NaN when we had one as input, although -- they may have been generated in a completely different way. val = 0/0 end ret[#ret + 1] = val end return ret end

--[[

-- intersection -- -- This returns the intersection of the values of n tables, as an array. For -- example, for the tables {1, 3, 4, 5, foo = 7} and {2, bar = 3, 5, 6}, -- intersection will return {3, 5}.

--]] function p.intersection(...) local vals, ret = {}, {} local lim = #tables for i = 1, select('#', ...) do local t = select(i, ...) for k, v in pairs(t) do if type(v) == 'number' and tostring(v) == '-nan' then v = nan -- NaN cannot be a table key, so use a proxy variable. end local valCount = vals[v] or 0 vals[v] = valCount + 1 end end for val, count in pairs(vals) do if count == lim then if val == nan then -- This ensures that we output a NaN when we had one as input, although -- they may have been generated in a completely different way. val = 0/0 end ret[#ret + 1] = val end end return ret end

--[[

-- numKeys -- -- This takes a table and returns an array containing the numbers of any numerical -- keys that have non-nil values, sorted in numerical order.

--]] function p.numKeys(t) local isPositiveInteger = p.isPositiveInteger local nums = {} for k, v in pairs(t) do if isPositiveInteger(k) then nums[#nums + 1] = k end end table.sort(nums) return nums end

--[[

-- affixNums -- -- This takes a table and returns an array containing the numbers of keys with the -- specified prefix and suffix. For example, for the table -- {a1 = 'foo', a3 = 'bar', a6 = 'baz'} and the prefix "a", affixNums will -- return {1, 3, 6}.

--]] function p.affixNums(t, prefix, suffix) prefix = prefix or suffix = suffix or local pattern = '^' .. prefix .. '([1-9]%d*)' .. suffix .. '\$' local nums = {} for k, v in pairs(t) do if type(k) == 'string' then local num = mw.ustring.match(k, pattern) if num then nums[#nums + 1] = tonumber(num) end end end table.sort(nums) return nums end

--[[

-- compressSparseArray -- -- This takes an array with one or more nil values, and removes the nil values -- while preserving the order, so that the array can be safely traversed with -- ipairs.

--]] function p.compressSparseArray(t) local ret = {} local nums = p.numKeys(t) for _, num in ipairs(nums) do ret[#ret + 1] = t[num] end return ret end

--[[

-- sparseIpairs -- -- This is an iterator for sparse arrays. It can be used like ipairs, but can -- handle nil values.

--]] function p.sparseIpairs(t) local nums = p.numKeys(t) local i = 0 local lim = #nums return function () i = i + 1 if i <= lim then local key = nums[i] return key, t[key] end end end

return p