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print: show inferred unit prices with at least 2 decimal places

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We don't do a good job of calculating good-looking unit prices when the
commodity display precisions are low. Eg when a journal doesn't use any
decimal places, any inferred unit prices are shown by the print command
also with no decimal places, which makes them look wrong.

Now inferred unit prices always have a minimum display precision of 2,
which helps a bit. Could do better.
This commit is contained in:
Simon Michael 2015-07-02 17:36:09 -07:00
parent a5295bd216
commit b735107f43
1 changed files with 20 additions and 14 deletions
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34
hledger-lib/Hledger/Data/Transaction.hs
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@ -311,9 +311,9 @@ inferBalancingAmount t@Transaction{tpostings=ps}
inferamount p = p
-- | Infer prices for this transaction's posting amounts, if needed to make
-- the postings balance. This is done once for the real postings and again
-- (separately) for the balanced virtual postings. When it's not possible, the
-- transaction is left unchanged.
-- the postings balance, and if possible. This is done once for the real
-- postings and again (separately) for the balanced virtual postings. When
-- it's not possible, the transaction is left unchanged.
--
-- The simplest example is a transaction with two postings, each in a
-- different commodity, with no prices specified. In this case we'll add a
@ -329,15 +329,21 @@ inferBalancingAmount t@Transaction{tpostings=ps}
-- There can also be more than two postings in either of the commodities.
--
-- We want to avoid excessive display of digits when the calculated price is
-- an irrational number, while also ensuring the displayed numbers balance if
-- the user does a manual calculation. This is achieved in two ways:
-- an irrational number, while hopefully also ensuring the displayed numbers
-- make sense if the user does a manual calculation. This is (mostly) achieved
-- in two ways:
--
-- - when there is only one posting in the "from" commodity, a total price
-- (@@) is used, and all available decimal digits are shown
--
-- - otherwise, a suitable averaged unit price (@) is applied to the relevant
-- postings, with a display precision that is the sum of the display
-- precisions of the two commodities being converted between.
-- postings, with display precision equal to the summed display precisions
-- of the two commodities being converted between, or 2, whichever is larger.
--
-- (We don't always calculate a good-looking display precision for unit prices
-- when the commodity display precisions are low, eg when a journal doesn't
-- use any decimal places. The minimum of 2 helps make the prices shown by the
-- print command a bit less surprising in this case. Could do better.)
--
-- All postings are expected to contain an explicit amount (no missing
-- amounts) in a single commodity. (The code used to avoid inferring prices
@ -373,14 +379,14 @@ priceInferrerFor t pt = inferprice
fromcommodity = head $ filter (`elem` sumcommodities) pcommodities -- these heads are ugly but should be safe
conversionprice
| fromcount==1 = TotalPrice $ abs toamount `withPrecision` maxprecision
| otherwise = UnitPrice $ abs unitprice `withPrecision` summedprecision
| otherwise = UnitPrice $ abs unitprice `withPrecision` unitprecision
where
fromcount = length $ filter ((==fromcommodity).acommodity) pamounts
fromamount = head $ filter ((==fromcommodity).acommodity) sumamounts
tocommodity = head $ filter (/=fromcommodity) sumcommodities
toamount = head $ filter ((==tocommodity).acommodity) sumamounts
unitprice = toamount `divideAmount` (aquantity fromamount)
summedprecision = (asprecision $ astyle $ toamount) + (asprecision $ astyle $ fromamount)
fromcount = length $ filter ((==fromcommodity).acommodity) pamounts
fromamount = head $ filter ((==fromcommodity).acommodity) sumamounts
tocommodity = head $ filter (/=fromcommodity) sumcommodities
toamount = head $ filter ((==tocommodity).acommodity) sumamounts
unitprice = toamount `divideAmount` (aquantity fromamount)
unitprecision = max 2 ((asprecision $ astyle $ toamount) + (asprecision $ astyle $ fromamount))
inferprice p = p
-- Get a transaction's secondary date, defaulting to the primary date.