mirror of
https://github.com/koreader/koreader
synced 2024-11-04 12:00:25 +00:00
129 lines
2.6 KiB
Lua
129 lines
2.6 KiB
Lua
--[[--
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Simple math helper functions
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]]
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local bit = require("bit")
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local dbg = require("dbg")
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local Math = {}
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local band = bit.band
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--[[--
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Rounds a percentage.
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@tparam float percent
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@treturn int rounded percentage
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]]
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function Math.roundPercent(percent)
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return math.floor(percent * 10000) / 10000
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end
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--[[--
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Rounds away from zero.
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@tparam float num
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@treturn int ceiled above 0, floored under 0
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]]
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function Math.roundAwayFromZero(num)
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if num > 0 then
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return math.ceil(num)
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else
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return math.floor(num)
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end
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end
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--[[--
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Rounds a number.
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No support for decimal points.
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@tparam float num
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@treturn int rounded number
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]]
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function Math.round(num)
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return math.floor(num + 0.5)
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end
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--[[--
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Determines if a number is odd or even.
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@int number
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@treturn string "odd" or "even"
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]]
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function Math.oddEven(number)
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if band(number, 1) == 1 then
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return "odd"
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else
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return "even"
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end
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end
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local function tmin_max(tab, func, op)
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if #tab == 0 then return nil, nil end
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local index, value = 1, tab[1]
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for i = 2, #tab do
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if func then
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if func(value, tab[i]) then
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index, value = i, tab[i]
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end
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elseif op == "min" then
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if value > tab[i] then
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index, value = i, tab[i]
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end
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elseif op == "max" then
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if value < tab[i] then
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index, value = i, tab[i]
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end
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end
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end
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return index, value
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end
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--[[--
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Returns the minimum element of a table.
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The optional argument func specifies a one-argument ordering function.
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@tparam table tab
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@tparam func func
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@treturn dynamic minimum element of a table
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]]
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function Math.tmin(tab, func)
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return tmin_max(tab, func, "min")
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end
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--[[--
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Returns the maximum element of a table.
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The optional argument func specifies a one-argument ordering function.
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@tparam table tab
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@tparam func func
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@treturn dynamic maximum element of a table
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]]
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function Math.tmax(tab, func)
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return tmin_max(tab, func, "max")
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end
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--[[--
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Restricts a value within an interval.
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@number value
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@number min
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@number max
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@treturn number value clamped to the interval [min,max]
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]]
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function Math.clamp(value, min, max)
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if value <= min then
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return min
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elseif value >= max then
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return max
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end
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return value
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end
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dbg:guard(Math, "minmax",
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function(value, min, max)
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assert(min ~= nil and max ~= nil, "Math.clamp: min " .. min .. " and max " .. nil .. " must not be nil")
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assert(min < max, "Math.clamp: min .. " .. min .. " must be less than max " .. max)
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end)
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return Math
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