implemented centre

src/Mtlstats/Format.hs

@@ -23,6 +23,7 @@ module Mtlstats.Format
   ( padNum
   , left
   , right
+  , centre
   ) where
 
 -- | Pad an 'Int' with leading zeroes to fit a certain character width
@@ -58,3 +59,16 @@ right
   -- ^ The text to align
   -> String
 right n str = reverse $ left n $ reverse str
+
+-- | Aligns text to the centre within a field (clipping if necessary)
+centre
+  :: Int
+  -- ^ The width of the field
+  -> String
+  -- ^ The text to align
+  -> String
+centre n str = let
+  sLen = length str
+  pLen = (n - sLen) `div` 2
+  pad  = replicate pLen ' '
+  in take n $ pad ++ str ++ repeat ' '

test/FormatSpec.hs

@@ -30,6 +30,7 @@ spec = describe "Mtlstats.Format" $ do
   padNumSpec
   leftSpec
   rightSpec
+  centreSpec
 
 padNumSpec :: Spec
 padNumSpec = describe "padNum" $ do
@@ -75,3 +76,14 @@ rightSpec = describe "right" $ do
   context "overflow" $
     it "should truncate the text" $
       right 2 "foo" `shouldBe` "oo"
+
+centreSpec :: Spec
+centreSpec = describe "centre" $ do
+
+  context "fit" $
+    it "should pad the text" $
+      centre 5 "foo" `shouldBe` " foo "
+
+  context "overflow" $
+    it "should truncate the text" $
+      centre 2 "foo" `shouldBe` "fo"