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koreader/frontend/optmath.lua

129 lines
2.6 KiB
Lua

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