register: --average/-A shows a running average, like ledger

MANUAL.md

@@ -720,15 +720,17 @@ summary postings within each interval:
     $ hledger register --monthly rent
     $ hledger register --monthly -E food --depth 4
 
+The `--average`/`-A` flag shows a running average instead of the running total.
+
+The `--related`/`-r` flag shows the *other* postings in the transactions
+of the postings which would normally be shown.
+
 The `--width`/`-w` option adjusts the width of the output. By default,
 this is 80 characters. To allow more space for descriptions and account
 names, use `-w` to increase the width to 120 characters, or `-wN` to set
 any desired width (at least 50 recommended, with no space before the N -
 eg `-w200` or `--width=200`,
 
-The `--related`/`-r` flag shows the *other* postings in the transactions
-of the postings which would normally be shown.
-
 #### balance
 
 The balance command displays accounts and their balances, indented to show the account hierarchy.

NEWS.md

@@ -6,6 +6,7 @@ title: hledger news
 
 ## unreleased
 
+- register: `--average/-A` shows a running average, like ledger
 - queries: `sym:REGEXP` matches (whole) commodity symbols
 - queries: `amt` now uses the = operator by default, eg amt:50 finds amounts equal to 50
 - don't break when there are non-ascii characters in CSV files

hledger-lib/Hledger/Reports.hs

@@ -94,6 +94,7 @@ data ReportOpts = ReportOpts {
     ,yearly_         :: Bool
     ,format_         :: Maybe FormatStr
     ,related_        :: Bool
+    ,average_        :: Bool
     ,query_          :: String -- all arguments, as a string
  } deriving (Show)
 
@@ -124,6 +125,7 @@ defreportopts = ReportOpts
     def
     def
     def
+    def
 
 instance Default ReportOpts where def = defreportopts
 
@@ -254,14 +256,14 @@ type PostingsReport = (String               -- label for the running balance col
 type PostingsReportItem = (Maybe Day    -- posting date, if this is the first posting in a transaction or if it's different from the previous posting's date
                           ,Maybe String -- transaction description, if this is the first posting in a transaction
                           ,Posting      -- the posting, possibly with account name depth-clipped
-                          ,MixedAmount  -- the running total after this posting
+                          ,MixedAmount  -- the running total after this posting (or with --average, the running average)
                           )
 
 -- | Select postings from the journal and add running balance and other
 -- information to make a postings report. Used by eg hledger's register command.
 postingsReport :: ReportOpts -> Query -> Journal -> PostingsReport
 postingsReport opts q j = -- trace ("q: "++show q++"\nq': "++show q') $
-                          (totallabel, postingsReportItems ps nullposting wd depth startbal (+))
+                          (totallabel, postingsReportItems ps nullposting wd depth startbal runningcalcfn 1)
     where
       ps | interval == NoInterval = displayableps
          | otherwise              = summarisePostingsByInterval interval depth empty reportspan displayableps
@@ -293,14 +295,16 @@ postingsReport opts q j = -- trace ("q: "++show q++"\nq': "++show q') $
       reportspan | empty     = requestedspan `orDatesFrom` journalspan
                  | otherwise = requestedspan `spanIntersect` matchedspan
       startbal = sumPostings precedingps
+      runningcalcfn | average_ opts = \i avg amt -> avg + (amt - avg) `divideMixedAmount` (fromIntegral i)
+                    | otherwise     = \_ bal amt -> bal + amt
 
 totallabel = "Total"
 balancelabel = "Balance"
 
 -- | Generate postings report line items.
-postingsReportItems :: [Posting] -> Posting -> WhichDate -> Int -> MixedAmount -> (MixedAmount -> MixedAmount -> MixedAmount) -> [PostingsReportItem]
-postingsReportItems [] _ _ _ _ _ = []
-postingsReportItems (p:ps) pprev wd d b sumfn = i:(postingsReportItems ps p wd d b' sumfn)
+postingsReportItems :: [Posting] -> Posting -> WhichDate -> Int -> MixedAmount -> (Int -> MixedAmount -> MixedAmount -> MixedAmount) -> Int -> [PostingsReportItem]
+postingsReportItems [] _ _ _ _ _ _ = []
+postingsReportItems (p:ps) pprev wd d b runningcalcfn itemnum = i:(postingsReportItems ps p wd d b' runningcalcfn (itemnum+1))
     where
       i = mkpostingsReportItem showdate showdesc wd p' b'
       showdate = isfirstintxn || isdifferentdate
@@ -309,7 +313,7 @@ postingsReportItems (p:ps) pprev wd d b sumfn = i:(postingsReportItems ps p wd d
       isdifferentdate = case wd of PrimaryDate   -> postingDate p  /= postingDate pprev
                                    SecondaryDate -> postingDate2 p /= postingDate2 pprev
       p' = p{paccount=clipAccountName d $ paccount p}
-      b' = b `sumfn` pamount p
+      b' = runningcalcfn itemnum b (pamount p)
 
 -- | Generate one postings report line item, containing the posting,
 -- the current running balance, and optionally the posting date and/or

hledger/Hledger/Cli/Options.hs

@@ -215,6 +215,7 @@ postingsmode = (commandmode ["register","postings"]) {
  ,modeGroupFlags = Group {
      groupUnnamed = [
       flagOpt (show defaultWidthWithFlag) ["width","w"] (\s opts -> Right $ setopt "width" s opts) "N" "increase or set the output width (default: 80)"
+     ,flagNone ["average","A"] (\opts -> setboolopt "average" opts) "show the running average instead of the running total"
      ,flagNone ["related","r"] (\opts -> setboolopt "related" opts) "show the other postings in the transactions of those that would have been shown"
      ]
     ,groupHidden = []
@@ -350,6 +351,7 @@ toCliOpts rawopts = do
                             ,quarterly_ = boolopt "quarterly" rawopts
                             ,yearly_    = boolopt "yearly" rawopts
                             ,format_    = maybestringopt "format" rawopts
+                            ,average_   = boolopt "average" rawopts  -- register
                             ,related_   = boolopt "related" rawopts  -- register
                             ,query_     = unwords $ listofstringopt "args" rawopts
                             }