Fixed #191. Non-breaking spaces in show output.

CHANGELOG.md

@@ -1,3 +1,8 @@
+1.3
+-------------
+* Breaking: Changed the `Show` instances for `UnitName`, `Unit`, `SQuantity` to use non-breaking spaces
+  within unit names and between values and their units.
+
 1.2 (2018-11)
 -------------
 * Add `NoStarIsType` extension and import `Data.Kind.Type` for [GHC 8.6 compitbility](https://github.com/ghc-proposals/ghc-proposals/blob/05721788de9ab6538def68c3c2c9dec50c9f24a8/proposals/0020-no-type-in-type.rst). Abandon compatibility with GHC < 8.

src/Numeric/Units/Dimensional.hs

@@ -411,7 +411,7 @@ Multiplication, division and powers apply to both units and quantities.
 -- | Forms the reciprocal of a 'Quantity', which has the reciprocal dimension.
 --
 -- >>> recip $ 47 *~ hertz
--- 2.127659574468085e-2 s
+-- 2.127659574468085e-2 s
 recip :: (Fractional a) => Quantity d a -> Quantity (Recip d) a
 recip = liftQ Prelude.recip
 
@@ -550,10 +550,10 @@ infixl 7  *~~, /~~
 -- | The sum of all elements in a foldable structure.
 --
 -- >>> sum ([] :: [Mass Double])
--- 0.0 kg
+-- 0.0 kg
 --
 -- >>> sum [12.4 *~ meter, 1 *~ foot]
--- 12.7048 m
+-- 12.7048 m
 sum :: (Num a, Foldable f) => f (Quantity d a) -> Quantity d a
 sum = foldr (+) _0
 
@@ -716,7 +716,7 @@ If you feel your work requires this instance, it is provided as an orphan in "Nu
 --
 -- >>> let x = (37 :: Rational) *~ poundMass
 -- >>> changeRep x :: Mass Double
--- 16.78291769 kg
+-- 16.78291769 kg
 changeRep :: (KnownVariant v, Real a, Fractional b) => Dimensional v d a -> Dimensional v d b
 changeRep = dmap realToFrac
 

src/Numeric/Units/Dimensional/Float.hs

@@ -104,7 +104,7 @@ isNegativeZero = P.isNegativeZero . unQuantity
 --
 -- >>> let x = 3 *~ meter
 -- >>> scaleFloat 3 x
--- 24.0 m
+-- 24.0 m
 scaleFloat :: RealFloat a => Int -> Quantity d a -> Quantity d a
 scaleFloat x = Quantity . P.scaleFloat x . unQuantity
 

src/Numeric/Units/Dimensional/Internal.hs

@@ -227,6 +227,7 @@ We will conclude by providing a reasonable 'Show' instance for
 quantities. The SI unit of the quantity is inferred
 from its dimension.
 -}
+-- | Uses non-breaking spaces between the value and the unit, and within the unit name.
 instance (KnownDimension d, E.KnownExactPi s, Show a, Real a) => Show (SQuantity s d a) where
   show (Quantity x) | isExactOne s' = show x ++ showName n
                     | otherwise = "Quantity " ++ show x ++ " {- " ++ show q ++ " -}"
@@ -238,15 +239,18 @@ instance (KnownDimension d, E.KnownExactPi s, Show a, Real a) => Show (SQuantity
 
 -- | Shows the value of a 'Quantity' expressed in a specified 'Unit' of the same 'Dimension'.
 --
--- >>> showIn watt $ (37 *~ volt) * (4 *~ ampere)
--- "148.0 W"
+-- Uses non-breaking spaces between the value and the unit, and within the unit name.
+--
+-- >>> putStrLn $ showIn watt $ (37 *~ volt) * (4 *~ ampere)
+-- 148.0 W
 showIn :: (Show a, Fractional a) => Unit m d a -> Quantity d a -> String
 showIn (Unit n _ y) (Quantity x) = show (x / y) ++ (showName . Name.weaken $ n)
 
 showName :: UnitName 'NonMetric -> String
 showName n | n == nOne = ""
-           | otherwise = " " ++ show n
+           | otherwise = "\xA0" ++ show n
 
+-- | Unit names are shown with non-breaking spaces.
 instance (Show a) => Show (Unit m d a) where
   show (Unit n e x) = "The unit " ++ show n ++ ", with value " ++ show e ++ " (or " ++ show x ++ ")"