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path: root/Master/texmf-dist/tex/generic/pgf/graphdrawing/lua/pgf/gd/planar/List.lua
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local List = {}

List.__index = List

function List.new()
	local t = {first = 0, last = -1}
	setmetatable(t, List)
	return t
end

function List:pushleft(value)
	local first = self.first - 1
	self.first = first
	self[first] = value
end

function List:pushright(value)
	local last = self.last + 1
	self.last = last
	self[last] = value
end

function List:popleft()
	local first = self.first
	if first > self.last then error("List is empty") end
	local value = self[first]
	self[first] = nil
	self.first = first + 1
	return value
end

function List:popright()
	local last = self.last
	if self.first > last then error("List is empty") end
	local value = self[last]
	self[last] = nil
	self.last = last - 1
	return value
end

function List:size()
	return self.last - self.first + 1
end

function List:empty()
	return self.last < self.first
end

return List