show numbers with thousands separator

Amount.hs

@@ -50,12 +50,22 @@ parseAmount s = nullamt
 
 showAmountRoundedOrZero :: Amount -> String
 showAmountRoundedOrZero (Amount cur qty) =
-    let rounded = printf "%.2f" qty in
+    let rounded = punctuatethousands $ printf "%.2f" qty in
     case rounded of
       "0.00"    -> "0"
       "-0.00"   -> "0"
       otherwise -> (symbol cur) ++ rounded
 
+punctuatethousands :: String -> String
+punctuatethousands s =
+    sign ++ (punctuate int) ++ frac
+    where 
+      (sign,num) = break isDigit s
+      (int,frac) = break (=='.') num
+      punctuate = reverse . concat . intersperse "," . triples . reverse
+      triples "" = []
+      triples s = [take 3 s] ++ (triples $ drop 3 s)
+
 instance Num Amount where
     abs (Amount c q) = Amount c (abs q)
     signum (Amount c q) = Amount c (signum q)

NOTES

@@ -3,7 +3,6 @@ hledger project notes
 * TO DO
 ** bugs
 ** compatibility
-*** , in thousands
 *** use greatest precision in register
 *** abbreviate 0
 *** don't combine entries so much in register

Tests.hs

@@ -294,13 +294,16 @@ quickcheck = mapM quickCheck ([
         ] :: [Bool])
 
 hunit = runTestTT $ "hunit" ~: test ([
-         "" ~: parseLedgerPatternArgs []                     @=? ([],[])
-        ,"" ~: parseLedgerPatternArgs ["a"]                  @=? (["a"],[])
-        ,"" ~: parseLedgerPatternArgs ["a","b"]              @=? (["a","b"],[])
-        ,"" ~: parseLedgerPatternArgs ["a","b","--"]         @=? (["a","b"],[])
-        ,"" ~: parseLedgerPatternArgs ["a","b","--","c","b"] @=? (["a","b"],["c","b"])
-        ,"" ~: parseLedgerPatternArgs ["--","c"]             @=? ([],["c"])
-        ,"" ~: parseLedgerPatternArgs ["--"]                 @=? ([],[])
+         "" ~: parseLedgerPatternArgs []                     @?= ([],[])
+        ,"" ~: parseLedgerPatternArgs ["a"]                  @?= (["a"],[])
+        ,"" ~: parseLedgerPatternArgs ["a","b"]              @?= (["a","b"],[])
+        ,"" ~: parseLedgerPatternArgs ["a","b","--"]         @?= (["a","b"],[])
+        ,"" ~: parseLedgerPatternArgs ["a","b","--","c","b"] @?= (["a","b"],["c","b"])
+        ,"" ~: parseLedgerPatternArgs ["--","c"]             @?= ([],["c"])
+        ,"" ~: parseLedgerPatternArgs ["--"]                 @?= ([],[])
+        ,"" ~: punctuatethousands "" @?= ""
+        ,"" ~: punctuatethousands "1234567.8901" @?= "1,234,567.8901"
+        ,"" ~: punctuatethousands "-100" @?= "-100"
         ,"" ~: test_ledgertransaction
         ,"" ~: test_ledgerentry
         ,"" ~: test_autofillEntry

Utils.hs

@@ -1,6 +1,7 @@
 -- standard imports and utilities
 module Utils (
               module Utils,
+              module Char,
               module Data.List,
               module Data.Tree,
               module Text.Printf,
@@ -10,6 +11,7 @@ module Utils (
               module Test.HUnit
              )
 where
+import Char
 import Data.List
 import Data.Tree
 import Text.Printf