Module:TableTools

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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