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https://github.com/SpaceVim/SpaceVim.git
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117 lines
2.2 KiB
Lua
117 lines
2.2 KiB
Lua
local M = {}
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Deque = {}
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Deque.__index = Deque
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---@class Deque
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---A double ended queue
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---
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---@return Deque
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function Deque.new()
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-- the indexes are created with an offset so that the indices are consequtive
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-- otherwise, when both pushleft and pushright are used, the indices will have a 1 length hole in the middle
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return setmetatable({ first = 0, last = -1 }, Deque)
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end
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---push to the left of the deque
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---@param value any
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function Deque:pushleft(value)
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local first = self.first - 1
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self.first = first
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self[first] = value
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end
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---push to the right of the deque
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---@param value any
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function Deque:pushright(value)
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local last = self.last + 1
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self.last = last
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self[last] = value
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end
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---pop from the left of the deque
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---@return any
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function Deque:popleft()
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local first = self.first
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if first > self.last then
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return nil
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end
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local value = self[first]
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self[first] = nil -- to allow garbage collection
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self.first = first + 1
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return value
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end
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---pops from the right of the deque
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---@return any
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function Deque:popright()
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local last = self.last
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if self.first > last then
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return nil
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end
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local value = self[last]
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self[last] = nil -- to allow garbage collection
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self.last = last - 1
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return value
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end
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---checks if the deque is empty
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---@return boolean
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function Deque:is_empty()
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return self:len() == 0
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end
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---returns the number of elements of the deque
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---@return number
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function Deque:len()
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return self.last - self.first + 1
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end
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---returns and iterator of the indices and values starting from the left
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---@return function
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function Deque:ipairs_left()
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local i = self.first
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return function()
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local res = self[i]
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local idx = i
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if res then
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i = i + 1
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return idx, res
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end
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end
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end
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---returns and iterator of the indices and values starting from the right
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---@return function
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function Deque:ipairs_right()
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local i = self.last
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return function()
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local res = self[i]
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local idx = i
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if res then
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i = i - 1 -- advance the iterator before we return
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return idx, res
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end
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end
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end
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---removes all values from the deque
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---@return nil
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function Deque:clear()
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for i, _ in self:ipairs_left() do
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self[i] = nil
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end
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self.first = 0
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self.last = -1
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end
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M.Deque = Deque
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return M
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