add L scale!

src/Scales.hs

@@ -1,8 +1,31 @@
 {-# Language DataKinds #-}
-module Scales where
+{- |
+
+The scales and guage marks found on a Concise #300 circular slide rule.
+
+-}
+module Scales (
+  cScale,
+  ciScale,
+  dScale,
+  kScale,
+  t1Scale,
+  t2Scale,
+  sScale,
+  ll2Scale,
+  ll3Scale,
+  lScale,
+) where
 
 import SlideRule
 
+lScale :: Scale OnWheel
+lScale = Scale
+  { scaleName = "L"
+  , scaleFun = id
+  , scaleFun' = id
+  }
+
 cScale :: Scale OnWheel
 cScale = Scale
   { scaleName = "C"
@@ -89,3 +112,19 @@ degToRad x = x * pi / 180
 
 radToDeg :: Double -> Double
 radToDeg x = x * 180 / pi
+
+-- | pi
+π :: Double
+π = pi
+
+-- | degrees per radian
+ρ :: Double
+ρ = 18/pi
+
+-- | minutes per radian
+ρ' :: Double
+ρ' = 10.8/pi
+
+-- | seconds per radian
+ρ'' :: Double
+ρ'' = 6.48/pi