Difference between revisions of "Module:TableTools"

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(start module with useful tools for dealing with Lua tables)
 
(add getNumKeys function and improve the comments, add the beginnings of a sparseIpairs function)
Line 9: Line 9:
 
--[[
 
--[[
 
-----------------------------------------------------------------------------------
 
-----------------------------------------------------------------------------------
-- Helper functions
+
-- 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)
local function isPositiveInteger(num)
 
-- Returns true if the given number is a positive integer, and false if not.
 
 
if type(num) == 'number' and num >= 1 and floor(num) == num and num < infinity then
 
if type(num) == 'number' and num >= 1 and floor(num) == num and num < infinity then
 
return true
 
return true
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return false
 
return false
 
end
 
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
 
end
  
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--]]
 
--]]
 
function p.compressSparseArray(t)
 
function p.compressSparseArray(t)
local nums, ret = {}, {}
+
local ret = {}
for k, v in pairs(t) do
+
local nums = p.getNumKeys(t)
if isPositiveInteger(k) then
 
nums[#nums + 1] = k
 
end
 
end
 
 
table.sort(nums)
 
table.sort(nums)
 
for _, num in ipairs(nums) do
 
for _, num in ipairs(nums) do
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return ret
 
return ret
 
end
 
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
 
return p

Revision as of 13:33, 15 December 2013

-- 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