ギヤ比

ソースコード
https://github.com/index333/gear

ギヤ比は一般には単に前後の比率で表します。
例えばフロント３０T　ｘ　リヤ２０Tの場合
３０➗２０で１．５０

欧米では伝統的にダルマ型自転車の前輪径に換算します。
３０ｘ２０の場合
２７ｘ１．５＝４１インチギヤ
のように表現します。
欧米式の利点は小径車にも統一的に使えることです。
上の場合
２０ｘ１．５＝３０インチギヤとなります。
逆にロードレーサーの４１インチギヤと同じ速度を小径車で得るには
３０ｘ１５あるいは３９ｘ２０という前後の組み合わせが必要となります。

---

ケーデンスを固定した時の時速で表したほうが直感的と思います。

まずタイヤ周長を選択します。

	import Graphics.UI.Gtk
	main = do
	c <- getContents
	let texts = lines c
	initGUI
	w <- windowNew
	w `set` [windowDefaultWidth := 1000, windowDefaultHeight := 800]
	sw <- scrolledWindowNew Nothing Nothing
	vb <- vBoxNew True 0
	bs <- mapM (buttonNewWithLabel) texts
	mapM_ (\b -> b `set` [buttonXalign := 0, buttonYalign := 0]) bs
	mapM_ (\b -> (b `on` buttonActivated) (func b)) bs
	mapM_ (containerAdd vb) bs
	scrolledWindowAddWithViewport sw vb
	containerAdd w sw
	widgetShowAll w
	(w `on`unrealize) mainQuit
	mainGUI
	func b = b `get` buttonLabel >>= putStrLn >> mainQuit

view raw selectItem.hs hosted with ❤ by GitHub

データはキャットアイのページからコピーしました。

$ cat tires
18-622 700x18C 2070 207
19-622 700x19C 2080 208
20-622 700x20C 2086 209
23-622 700x23C 2096 210
25-622 700x25C 2105 211
28-622 700x28C 2136 214
30-622 700x30C 2146 215
32-622 700x32C 2155 216
xx-xxx  Tubular 2130 213
35-622 700x35C 2168 217
38-622 700x38C 2180 218
40-622 700x40C 2200 220
42-622 700x42C 2224 222
44-622 700x44C 2235 224
45-622 700x45C 2242 224
47-622 700x47C 2268 227

＄　cat tires | runghc selectItem.hs > tmp
$ cat tmp
23-622 700x23C 2096 210

	import Graphics.UI.Gtk
	import MySpinBox
	import Round
	main = do
	c <- getContents
	let [_,_,a,_] = words c
	let t = read a :: Double
	let names = ["タイヤ周長(mm)",
	"frontA(T)",
	"frontB(T)",
	"最大コグ(T)",
	"cadens(/m)"]
	let spmods = [(t,2000,2300,1,10),
	(39,20,60,1,10),
	(52,20,60,1,10),
	(23,21,32,1,10),
	(90,50,160,1,10)]
	initGUI
	window <- windowNew
	hbox <- hBoxNew False 0
	vbox <- vBoxNew False 0
	boxPackStart vbox hbox PackNatural 0
	adjs <- mkAdjustments spmods
	update adjs
	spins <- myAddSpinButtons hbox names adjs
	mapM_ (`set` [spinButtonDigits := 0]) spins
	mapM_ (flip onValueChanged (update adjs)) adjs
	containerAdd window vbox
	widgetShowAll window
	window `on` unrealize $ mainQuit
	mainGUI
	update adjs = do
	l:fa:fb:m:c:_ <- mapM (`get` adjustmentValue) adjs
	putStr "タイヤ周長(mm) = "
	print l
	mapM_ (disp l fa fb c) [11..m]
	disp l fa fb c x = do
	disp' l fa x c
	putStr " "
	disp' l fb x c
	putStrLn ""
	disp' l f r c = do
	putStr $ show $ round f
	putStr "x"
	putStr $ show $ round r
	putStr "="
	putStr $ show (kph l f r c)
	putStr "km/h "
	kph l f r c = round1 $ (l/1000^2) * (f / r) * (c * 60)

view raw gear.hs hosted with ❤ by GitHub

---

Round モジュール、MySpinBox　モジュールが必要です。

	module Round where
	roundN :: Int -> Double -> Double
	roundN n d = fromIntegral (round (d * 10 ^ n)) / fromIntegral (10 ^ n)
	round1,round2 :: Double -> Double
	round1 = roundN 1
	round2 = roundN 2

view raw Round.hs hosted with ❤ by GitHub

	module MySpinBox where
	import Graphics.UI.Gtk
	import Control.Monad
	mkAdjustment :: (Double, Double, Double, Double, Double) -> IO Adjustment
	mkAdjustment (v,l,u,s,p) = adjustmentNew v l u s p 0
	{-
	:: Double value - the initial value.
	-> Double lower - the minimum value.
	-> Double upper - the maximum value.
	-> Double stepIncrement - the step increment.
	-> Double pageIncrement - the page increment.
	-> Double pageSize - the page size.
	-}
	mkAdjustments :: [(Double, Double, Double, Double, Double)] ->
	IO [Adjustment]
	mkAdjustments = mapM mkAdjustment
	myAddSpinButtons :: HBox -> [String] ->[Adjustment] -> IO [SpinButton]
	myAddSpinButtons box names adjustments = do
	zipWithM (\x y -> myAddSpinButton box x y) names adjustments
	myAddSpinButton :: HBox -> String -> Adjustment -> IO SpinButton
	myAddSpinButton box name adj = do
	vbox <- vBoxNew False 0
	boxPackStart box vbox PackRepel 0
	label <- labelNew (Just name)
	miscSetAlignment label 0.0 0.5
	boxPackStart vbox label PackNatural 0
	spinb <- spinButtonNew adj 10 1
	boxPackStart vbox spinb PackGrow 0
	return spinb

view raw MySpinBox.hs hosted with ❤ by GitHub

$ cat tmp | runghc gear.hs