97 lines
2.1 KiB
Lua
97 lines
2.1 KiB
Lua
---------------------------------------------------------------------------
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-- Various math related functions.
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--
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--- Math module for gears.
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--
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-- @utillib gears.math
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---------------------------------------------------------------------------
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local rtable = table
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local gmath = {}
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local function subset_mask_apply(mask, set)
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local ret = {}
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for i = 1, #set do
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if mask[i] then
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rtable.insert(ret, set[i])
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end
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end
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return ret
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end
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local function subset_next(mask)
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local i = 1
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while i <= #mask and mask[i] do
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mask[i] = false
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i = i + 1
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end
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if i <= #mask then
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mask[i] = 1
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return true
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end
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return false
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end
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--- Return all subsets of a specific set.
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-- This function, giving a set, will return all subset it.
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-- For example, if we consider a set with value { 10, 15, 34 },
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-- it will return a table containing 2^n set:
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-- { }, { 10 }, { 15 }, { 34 }, { 10, 15 }, { 10, 34 }, etc.
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-- @param set A set.
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-- @return A table with all subset.
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-- @staticfct gears.math.subsets
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function gmath.subsets(set)
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local mask = {}
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local ret = {}
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for i = 1, #set do mask[i] = false end
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-- Insert the empty one
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rtable.insert(ret, {})
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while subset_next(mask) do
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rtable.insert(ret, subset_mask_apply(mask, set))
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end
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return ret
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end
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--- Make i cycle.
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-- @param t A length. Must be greater than zero.
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-- @param i An absolute index to fit into #t.
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-- @return An integer in (1, t) or nil if t is less than or equal to zero.
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-- @staticfct gears.math.cycle
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function gmath.cycle(t, i)
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if t < 1 then return end
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i = i % t
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if i == 0 then
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i = t
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end
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return i
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end
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--- Round a number to an integer.
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-- @tparam number x
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-- @treturn integer
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-- @staticfct gears.math.round
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function gmath.round(x)
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return math.floor(x + 0.5)
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end
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--- Return the sign of the number x
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-- return 1 if x is positive, -1 if negative and 0 if x is 0
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-- @tparam number x
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-- @treturn integer
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-- @staticfct gears.math.sign
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function gmath.sign(x)
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if x > 0 then
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return 1
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elseif x < 0 then
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return -1
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else
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return 0
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end
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end
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return gmath
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