Module:TableTools: Difference between revisions

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    Revision as of 11:44, 24 June 2018

    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 libraryUtil = require('libraryUtil')
    
    local p = {}
    
    -- Define often-used variables and functions.
    local floor = math.floor
    local infinity = math.huge
    local checkType = libraryUtil.checkType
    
    --[[
    ------------------------------------------------------------------------------------
    -- isPositiveInteger
    --
    -- This function returns true if the given value 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(v)
    	if type(v) == 'number' and v >= 1 and floor(v) == v and v < infinity then
    		return true
    	else
    		return false
    	end
    end
    
    --[[
    ------------------------------------------------------------------------------------
    -- isNan
    --
    -- This function returns true if the given number is a NaN value, and false
    -- if not. Although it doesn't operate on tables, it is included here as it is
    -- useful for determining whether a value can be a valid table key. Lua will
    -- generate an error if a NaN is used as a table key.
    ------------------------------------------------------------------------------------
    --]]
    function p.isNan(v)
    	if type(v) == 'number' and tostring(v) == '-nan' then
    		return true
    	else
    		return false
    	end
    end
    
    --[[
    ------------------------------------------------------------------------------------
    -- shallowClone
    --
    -- This returns a clone of a table. The value returned is a new table, but all
    -- subtables and functions are shared. Metamethods are respected, but the returned
    -- table will have no metatable of its own.
    ------------------------------------------------------------------------------------
    --]]
    function p.shallowClone(t)
    	local ret = {}
    	for k, v in pairs(t) do
    		ret[k] = v
    	end
    	return ret
    end
    
    --[[
    ------------------------------------------------------------------------------------
    -- removeDuplicates
    --
    -- This removes duplicate values from an array. Non-positive-integer keys are
    -- ignored. The earliest value is kept, and all subsequent duplicate values are
    -- removed, but otherwise the array order is unchanged.
    ------------------------------------------------------------------------------------
    --]]
    function p.removeDuplicates(t)
    	checkType('removeDuplicates', 1, t, 'table')
    	local isNan = p.isNan
    	local ret, exists = {}, {}
    	for i, v in ipairs(t) do
    		if isNan(v) then
    			-- NaNs can't be table keys, and they are also unique, so we don't need to check existence.
    			ret[#ret + 1] = v
    		else
    			if not exists[v] then
    				ret[#ret + 1] = v
    				exists[v] = true
    			end
    		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)
    	checkType('numKeys', 1, t, 'table')
    	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)
    	checkType('affixNums', 1, t, 'table')
    	checkType('affixNums', 2, prefix, 'string', true)
    	checkType('affixNums', 3, suffix, 'string', true)
    
    	local function cleanPattern(s)
    		-- Cleans a pattern so that the magic characters ()%.[]*+-?^$ are interpreted literally.
    		s = s:gsub('([%(%)%%%.%[%]%*%+%-%?%^%$])', '%%%1')
    		return s
    	end
    
    	prefix = prefix or ''
    	suffix = suffix or ''
    	prefix = cleanPattern(prefix)
    	suffix = cleanPattern(suffix)
    	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
    
    --[[
    ------------------------------------------------------------------------------------
    -- numData
    --
    -- Given a table with keys like ("foo1", "bar1", "foo2", "baz2"), returns a table
    -- of subtables in the format 
    -- { [1] = {foo = 'text', bar = 'text'}, [2] = {foo = 'text', baz = 'text'} }
    -- Keys that don't end with an integer are stored in a subtable named "other".
    -- The compress option compresses the table so that it can be iterated over with
    -- ipairs.
    ------------------------------------------------------------------------------------
    --]]
    function p.numData(t, compress)
    	checkType('numData', 1, t, 'table')
    	checkType('numData', 2, compress, 'boolean', true)
    	local ret = {}
    	for k, v in pairs(t) do
    		local prefix, num = mw.ustring.match(tostring(k), '^([^0-9]*)([1-9][0-9]*)$')
    		if num then
    			num = tonumber(num)
    			local subtable = ret[num] or {}
    			if prefix == '' then
    				-- Positional parameters match the blank string; put them at the start of the subtable instead.
    				prefix = 1
    			end
    			subtable[prefix] = v
    			ret[num] = subtable
    		else
    			local subtable = ret.other or {}
    			subtable[k] = v
    			ret.other = subtable
    		end
    	end
    	if compress then
    		local other = ret.other
    		ret = p.compressSparseArray(ret)
    		ret.other = other
    	end
    	return ret
    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)
    	checkType('compressSparseArray', 1, t, 'table')
    	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)
    	checkType('sparseIpairs', 1, t, 'table')
    	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]
    		else
    			return nil, nil
    		end
    	end
    end
    
    --[[
    ------------------------------------------------------------------------------------
    -- size
    --
    -- This returns the size of a key/value pair table. It will also work on arrays,
    -- but for arrays it is more efficient to use the # operator.
    ------------------------------------------------------------------------------------
    --]]
    function p.size(t)
    	checkType('size', 1, t, 'table')
    	local i = 0
    	for k in pairs(t) do
    		i = i + 1
    	end
    	return i
    end
    
    return p