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3b69cf992e
* Installs luarocks WITH it's executable (easy to install other rocks if necessary) * Use Lua supplied with luarocks * Create Utils/luadocumentor.bat, which works with RELATIVE PATH ! -> Everybody can generate the doc * Updated launch files accordingly
66 lines
1.6 KiB
Lua
66 lines
1.6 KiB
Lua
--- Permutation operations.
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-- @class module
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-- @name pl.permute
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local tablex = require 'pl.tablex'
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local utils = require 'pl.utils'
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local copy = tablex.deepcopy
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local append = table.insert
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local coroutine = coroutine
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local resume = coroutine.resume
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local assert_arg = utils.assert_arg
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--[[
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module ('pl.permute',utils._module)
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]]
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local permute = {}
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-- PiL, 9.3
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local permgen
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permgen = function (a, n, fn)
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if n == 0 then
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fn(a)
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else
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for i=1,n do
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-- put i-th element as the last one
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a[n], a[i] = a[i], a[n]
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-- generate all permutations of the other elements
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permgen(a, n - 1, fn)
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-- restore i-th element
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a[n], a[i] = a[i], a[n]
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end
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end
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end
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--- an iterator over all permutations of the elements of a list.
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-- Please note that the same list is returned each time, so do not keep references!
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-- @param a list-like table
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-- @return an iterator which provides the next permutation as a list
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function permute.iter (a)
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assert_arg(1,a,'table')
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local n = #a
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local co = coroutine.create(function () permgen(a, n, coroutine.yield) end)
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return function () -- iterator
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local code, res = resume(co)
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return res
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end
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end
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--- construct a table containing all the permutations of a list.
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-- @param a list-like table
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-- @return a table of tables
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-- @usage permute.table {1,2,3} --> {{2,3,1},{3,2,1},{3,1,2},{1,3,2},{2,1,3},{1,2,3}}
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function permute.table (a)
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assert_arg(1,a,'table')
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local res = {}
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local n = #a
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permgen(a,n,function(t) append(res,copy(t)) end)
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return res
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end
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return permute
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