Module:TableTools

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    Revision as of 13:31, 15 December 2013 by m>Mr. Stradivarius (better variable name - getUnion deals with all tables, not just arrays)

    Documentation for this module may be created at Module:TableTools/doc

    --[[
    ------------------------------------------------------------------------------------
    --                               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
    
    --[[
    ------------------------------------------------------------------------------------
    -- 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
    
    --[[
    ------------------------------------------------------------------------------------
    -- getUnion
    --
    -- 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, 3, 5, bar = 6}, getUnion will return
    -- {1, 2, 3, 4, 5, 6, 7}.
    ------------------------------------------------------------------------------------
    --]]
    function p.getUnion(...)
    	local tables = {...}
    	local vals, ret = {}, {}
    	for _, t in ipairs(tables) do
    		for k, v in pairs(t) do
    			vals[v] = true
    		end
    	end
    	for val in pairs(vals) do
    		ret[#ret + 1] = val
    	end
    	table.sort(ret)
    end	
    
    --[[
    ------------------------------------------------------------------------------------
    -- getNumKeys
    --
    -- 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.getNumKeys(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
    
    --[[
    ------------------------------------------------------------------------------------
    -- getAffixNums
    --
    -- 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", getAffixNums will
    -- return {1, 3, 6}.
    ------------------------------------------------------------------------------------
    --]]
    function p.getAffixNums(t, prefix, suffix)
    	prefix = prefix or ''
    	suffix = suffix or ''
    	local nums = {}
    	for k, v in pairs(t) do
    		if type(k) == 'string' then			
    			local num = mw.ustring.match(k, '^' .. prefix .. '([1-9]%d*)' .. suffix .. '$')
    			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.getNumKeys(t)
    	table.sort(nums)
    	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.getNumKeys(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