Add decimalMark combinator to customize used decimal mark

Usage:

    > format (precision 3 <> decimalMark ',') pi
    "3,142"

Author: timhabermaas

Diff for: src/Text/Format.purs

@@ -7,6 +7,7 @@ module Text.Format
   , zeroFill
   , signed
   , precision
+  , decimalMark
   , class Format
   , format
   ) where
@@ -18,7 +19,7 @@ import Data.Unfoldable (replicate)
 import Data.Int as Int
 import Data.Maybe (Maybe(..), fromMaybe)
 import Data.Monoid (class Monoid)
-import Data.String (length, fromCharArray, dropWhile)
+import Data.String (length, fromCharArray, dropWhile, singleton, replace, Pattern(..), Replacement(..))
 import Math (round, pow, abs)
 
 -- | Pad a string on the left up to a given maximum length. The padding
@@ -32,6 +33,7 @@ type PropertiesRecord =
   , padChar :: Maybe Char
   , signed :: Maybe Boolean
   , precision :: Maybe Int
+  , decimalMark :: Maybe Char
   }
 
 default :: PropertiesRecord
@@ -40,6 +42,7 @@ default =
   , padChar: Nothing
   , signed: Nothing
   , precision: Nothing
+  , decimalMark: Nothing
   }
 
 data Properties = Properties PropertiesRecord
@@ -49,17 +52,19 @@ instance eqProperties :: Eq Properties where
     rec1.width     == rec2.width &&
     rec1.padChar   == rec2.padChar &&
     rec1.signed    == rec2.signed &&
-    rec1.precision == rec2.precision
+    rec1.precision == rec2.precision &&
+    rec1.decimalMark == rec2.decimalMark
 
 instance semigroupProperties :: Semigroup Properties where
   append (Properties rec1) (Properties rec2) = Properties rec
     where
       -- These are combined such that options to the right take precedence:
       -- width 3 <> width 4 == width 4
-      rec = { width:     rec2.width      <|> rec1.width
-            , padChar:   rec2.padChar    <|> rec1.padChar
-            , signed:    rec2.signed     <|> rec1.signed
-            , precision: rec2.precision  <|> rec1.precision
+      rec = { width:       rec2.width       <|> rec1.width
+            , padChar:     rec2.padChar     <|> rec1.padChar
+            , signed:      rec2.signed      <|> rec1.signed
+            , precision:   rec2.precision   <|> rec1.precision
+            , decimalMark: rec2.decimalMark <|> rec1.decimalMark
             }
 
 instance monoidProperties :: Monoid Properties where
@@ -82,6 +87,10 @@ signed = Properties (default { signed = Just true })
 precision :: Int -> Properties
 precision digits = Properties (default { precision = Just digits })
 
+-- | Delimiter character. Gets ignored for non-numeric types.
+decimalMark :: Char -> Properties
+decimalMark char = Properties (default { decimalMark = Just char })
+
 -- | A class for types that can be formatted using the specified properties.
 class Format a where
   format :: Properties -> a -> String
@@ -141,11 +150,15 @@ instance formatNumber :: Format Number where
      isSigned = fromMaybe false rec.signed
      padChar = fromMaybe ' ' rec.padChar
      nonNegative = num >= 0.0
-     numAbsStr' = show (abs num)
+     numAbsStr'' = show (abs num)
+     numAbsStr' = case rec.decimalMark of
+                    Nothing -> numAbsStr''
+                    Just d -> replace (Pattern ".") (Replacement (singleton d)) numAbsStr''
      numAbsStr = case rec.precision of
                    Nothing -> numAbsStr'
                    Just p -> numAbsStr' <> paddedZeros p
-     paddedZeros p = let d = length (dropWhile (_ /= '.') numAbsStr') - 1
+     usedDelimiter = fromMaybe '.' rec.decimalMark
+     paddedZeros p = let d = length (dropWhile (_ /= usedDelimiter) numAbsStr') - 1
                      in fromCharArray (replicate (p - d) '0')
      numSgn = if nonNegative
                 then (if isSigned then "+" else "")

Diff for: test/Main.purs

@@ -5,7 +5,7 @@ import Prelude
 import Data.Monoid (mempty)
 import Math (pi)
 
-import Text.Format (width, signed, zeroFill, precision, format)
+import Text.Format (width, signed, zeroFill, precision, decimalMark, format)
 
 import Control.Monad.Eff (Eff)
 import Control.Monad.Eff.Console (CONSOLE)
@@ -78,6 +78,9 @@ main = runTest do
     equal  "+123" $ format signed   123
     equal  "-123" $ format signed (-123)
 
+  test "Int: format (precision, decimalMark)" do
+    equal  "123,00" $ format (precision 2 <> decimalMark ',') 123
+
   test "Number: format" do
     equal  "3.14" $ format mempty   3.14
     equal "-3.14" $ format mempty (-3.14)
@@ -108,6 +111,10 @@ main = runTest do
     equal "3.0"     $ format (precision 1) 3
     equal "3.000"   $ format (precision 3) 3
 
+  test "Number: format (precision, decimalMark)" do
+    equal "3"       $ format (precision 0 <> decimalMark ',') pi
+    equal "3,1"     $ format (precision 1 <> decimalMark ',') pi
+
   test "Number: format (width, precision)" do
     equal "  3.14" $ format (width 6 <> precision 2) pi
     equal "     3" $ format (width 6 <> precision 0) pi
@@ -119,10 +126,15 @@ main = runTest do
     equal "+03.14" $ format (width 6 <> precision 2 <> signed <> zeroFill) pi
     equal "+3.142" $ format (width 6 <> precision 3 <> signed <> zeroFill) pi
 
+  test "Number: format (width, precision, signed, zeroFill, decimalMark)" do
+    equal "+03,14" $ format (width 6 <> precision 2 <> signed <> zeroFill <> decimalMark ',') pi
+    equal "+3,142" $ format (width 6 <> precision 3 <> signed <> zeroFill <> decimalMark ',') pi
+
   test "Handling of zero" do
     equal "0"      $ format mempty 0
     equal "0"      $ format (precision 0) 0.0
     equal "0.00"   $ format (precision 2) 0.0
+    equal "0,00"   $ format (precision 2 <> decimalMark ',') 0.0
     equal "+0"     $ format signed 0
     equal "+0.0"   $ format signed 0.0
     equal "+0.00"  $ format (signed <> precision 2) 0