70 lines
2.6 KiB
Lua
70 lines
2.6 KiB
Lua
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--[[
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Copyright (c) 2014, Robert 'Bobby' Zenz
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All rights reserved.
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Redistribution and use in source and binary forms, with or without
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modification, are permitted provided that the following conditions are met:
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* Redistributions of source code must retain the above copyright notice, this
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list of conditions and the following disclaimer.
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* Redistributions in binary form must reproduce the above copyright notice,
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this list of conditions and the following disclaimer in the documentation
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and/or other materials provided with the distribution.
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THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
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FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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--]]
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--- An implementation of the Fisher-Yates algorithm, which allows to access
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-- an array in a random or pseudo-random order.
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fisheryates = {}
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--- Runs the Fisher-Yates algorithm on the given data.
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--
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-- The given action method is invoked on each item, which means that the action
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-- method gets items in random order.
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--
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-- @param data The array on which to operate.
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-- @param min The minimum index of the array (inclusive).
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-- @param max The maximum index of the array (inclusive).
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-- @param random The method that returns random numbers, assumed to accept two
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-- parameters, a minimum and maximum value. Can also be a table
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-- with an instance method like the one descriped above.
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-- @param action The action to perform on each item. Assumed to accept two
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-- parameters, the item and the current index.
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function fisheryates.run(data, min, max, random, action)
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local random_is_object = type(random) == "userdata"
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for index = min, max, 1 do
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local swap_index = nil
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if random_is_object then
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swap_index = random:next(0, 32767)
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else
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swap_index = random(0, 32767)
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end
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swap_index = transform.linear(swap_index, 0, 32767, index, max)
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swap_index = mathutil.round(swap_index)
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local swap_value = data[swap_index]
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data[swap_index] = data[index]
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data[index] = swap_value
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action(data[index], index)
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end
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end
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