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2022-06-30T20:46:27Z

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www.mediawiki.org>ExE Boss: Prevent exponential expansion by performing all replacements during a single pass; goes from O(2ⁿ) to O(n)

2021-08-18T13:48:19Z

Prevent exponential expansion by performing all replacements during a single pass; goes from O(2ⁿ) to O(n)

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-- This is a helper module for {{tmpl}}
require('Module:No globals')

-- The trailing `[^0-9]?` ensures that `$10` doesn't potentially change
-- from being treated as `${1}0` to being treated as `${10}`
-- if the number of supported parameters is ever expanded:
local PATTERN = "%$([1-9])[^0-9]?"

local this = {}

function this.renderTmpl(frame)
local args = frame.args
local pargs = (frame:getParent() or {}).args
local input = pargs[0] or ''
local result = {}

local prevPos = 1
do
local startPos, _, k
while true do
startPos, _, k = string.find(input, PATTERN, prevPos)
if (not startPos) then break end
table.insert(result, string.sub(input, prevPos, startPos - 1))

local n = tonumber(k)
local r = pargs[n]
if (r) then
table.insert(result, r)
else
table.insert(result, '$' .. n)
end

prevPos = startPos + #k + 1
end
end

table.insert(result, string.sub(input, prevPos))
return table.concat(result)
end

return this

Module:Tmpl - Revision history

Stefanseiler: 1 revision imported

www.mediawiki.org>ExE Boss: Prevent exponential expansion by performing all replacements during a single pass; goes from O(2ⁿ) to O(n)