Module:TableTools

    From Nonbinary Wiki
    Revision as of 11:33, 15 December 2013 by m>Mr. Stradivarius (add getNumKeys function and improve the comments, add the beginnings of a sparseIpairs function)

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

    -- This module includes a number of functions that can be useful when dealing with Lua tables.
    
    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 the 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
    
    --[[
    -----------------------------------------------------------------------------------
    -- 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
    
    --[[
    -----------------------------------------------------------------------------------
    -- 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)
    
    return p