ab302f2 · rowtype-yoga/purescript-fixed-precision

git.iko.soy/rowtype-yoga/purescript-fixed-precision

on main help sign in

Fix String conversions with negatives #26 (#27)

ab302f2Harry Garrood7 years ago

src/Data/Fixed.purs+16−5

compare with main

unifiedsplit

@@ -44,6 +44,7 @@ import Data.BigInt as BigInt

44import Data.Int as Int

45import Data.Maybe (Maybe(..), fromJust)

46import Data.Monoid as Monoid

47+import Data.Ord (abs)

47import Data.String.CodeUnits as StringCU

48import Data.String.CodeUnits as StringCU

48import Data.String as String

49import Data.String as String

49import Math as Math

50import Math as Math

@@ -344,12 +345,19 @@ fromString

344 . KnownPrecision precision

345 . KnownPrecision precision

345 => String

346 => String

346 -> Maybe (Fixed precision)

347 -> Maybe (Fixed precision)

347−fromString str =

348+fromString str' =

348 let

349 let

349 numDigits = reflectPrecisionDecimalPlaces (PProxy :: PProxy precision)

350 numDigits = reflectPrecisionDecimalPlaces (PProxy :: PProxy precision)

350 denom = reflectPrecision (PProxy :: PProxy precision)

351 denom = reflectPrecision (PProxy :: PProxy precision)

351

352

352 isDigit = between '0' '9'

353 isDigit = between '0' '9'

354+

355+ { sign, str } =

356+ case String.stripPrefix (String.Pattern "-") str' of

357+ Just str ->

358+ { sign: negate one, str }

359+ Nothing ->

360+ { sign: one, str: str' }

353 wholeDigits = StringCU.countPrefix isDigit str

361 wholeDigits = StringCU.countPrefix isDigit str

354 { before, after } = StringCU.splitAt wholeDigits str

362 { before, after } = StringCU.splitAt wholeDigits str

355

363

@@ -365,7 +373,7 @@ fromString str =

365 guard (StringCU.charAt 0 after == Just '.')

373 guard (StringCU.charAt 0 after == Just '.')

366 let raw = StringCU.drop 1 after

374 let raw = StringCU.drop 1 after

367 BigInt.fromString (rightJustify numDigits '0' raw)

375 BigInt.fromString (rightJustify numDigits '0' raw)

368− pure (Fixed (wholePart * denom + fractionPart))

376+ pure (Fixed (sign * (wholePart * denom + fractionPart)))

369

377

370-- | Represent a `Fixed` value as a string, with the given number of decimal

378-- | Represent a `Fixed` value as a string, with the given number of decimal

371-- | places.

379-- | places.

@@ -392,10 +400,13 @@ toStringWithPrecision requestedDigits fixed@(Fixed n) =

392 let

400 let

393 denom = denominator fixed

401 denom = denominator fixed

394 denomDigits = reflectPrecisionDecimalPlaces (PProxy :: PProxy precision)

402 denomDigits = reflectPrecisionDecimalPlaces (PProxy :: PProxy precision)

403+ absNum = abs n

404+ -- Use 'quot' and 'rem' because we need to round towards zero

395− wholePart = n / denom

405+ wholePart = BigInt.quot absNum denom

396− fractionalPart = n `mod` denom

406+ fractionalPart = BigInt.rem absNum denom

397 in

407 in

408+ (if n < zero then "-" else "")

398− BigInt.toString wholePart

409+ <> BigInt.toString wholePart

399 <> Monoid.guard (requestedDigits > 0)

410 <> Monoid.guard (requestedDigits > 0)

400 ("." <>

411 ("." <>

401 rightJustify requestedDigits '0'

412 rightJustify requestedDigits '0'

test/Main.purs+13−9

@@ -2,7 +2,7 @@ module Test.Main where

3import Prelude

5−import Data.Fixed (class KnownPrecision, Fixed, PProxy, fromNumber, toNumber, fromString, reifyPrecision, reflectPrecision, toString, P100, rescale, fromBigInt, floor)

5+import Data.Fixed (class KnownPrecision, Fixed, PProxy, fromNumber, toNumber, fromString, reifyPrecision, reflectPrecision, toString, P100, rescale, fromBigInt, floor, ceil, numerator)

6import Data.BigInt as BigInt

7import Data.Maybe (Maybe(..), fromJust, isJust)

8import Effect (Effect)

@@ -10,14 +10,17 @@ import Effect.Console (log)

10import Math as Math

11import Partial.Unsafe (unsafePartial)

12import Test.QuickCheck (arbitrary, quickCheck', (<?>), (===))

13−import Test.QuickCheck.Gen (Gen, chooseInt, suchThat)

13+import Test.QuickCheck.Gen (Gen, chooseInt, uniform, suchThat)

15-- Just here to package up the safe use of `unsafePartial`.

16trying :: forall a b. Gen a -> (a -> Maybe b) -> Gen b

17trying gen f = map (unsafePartial fromJust) (map f gen `suchThat` isJust)

19genFixedP :: forall p. KnownPrecision p => PProxy p -> Gen (Fixed p)

20−genFixedP _ = map fromNumber arbitrary `trying` identity

20+genFixedP _ = map (fromNumber <<< stretch) uniform `trying` identity

21+ where

22+ -- maps [0,1] to [-10,10]

23+ stretch = (_ * 20.0) >>> (_ - 10.0)

22fromNumberWith

25fromNumberWith

23 :: forall precision

26 :: forall precision

@@ -35,15 +38,15 @@ withPrecisionOf

35 -> Fixed precision

38 -> Fixed precision

36withPrecisionOf _ x = x

39withPrecisionOf _ x = x

38−floorToPrecision

41+truncateToPrecision

39 :: forall precision

42 :: forall precision

40 . KnownPrecision precision

43 . KnownPrecision precision

41 => Int

44 => Int

42 -> Fixed precision

45 -> Fixed precision

43 -> Fixed precision

46 -> Fixed precision

44−floorToPrecision p =

47+truncateToPrecision p =

45 (_ / scaleFactor)

48 (_ / scaleFactor)

46− <<< floor

49+ <<< (\x -> if x > zero then floor x else ceil x)

47 <<< (_ * scaleFactor)

50 <<< (_ * scaleFactor)

48 where

51 where

49 scaleFactor =

52 scaleFactor =

@@ -123,7 +126,8 @@ main = do

123 precision <- chooseInt 0 100

126 precision <- chooseInt 0 100

124 unsafePartial fromJust $ reifyPrecision precision \p -> do

127 unsafePartial fromJust $ reifyPrecision precision \p -> do

125 a <- genFixedP p

128 a <- genFixedP p

126− pure $ fromString (toString a) == Just a <?> show { precision, a }

129+ let b = fromString (toString a)

130+ pure $ b == Just a <?> show { precision, a, b, numeratorA: numerator a, numeratorB: map numerator b }

127

131

128 log ""

132 log ""

129 log "Conversions to/from Number"

133 log "Conversions to/from Number"

@@ -162,7 +166,7 @@ main = do

162 let xx = rescale y

166 let xx = rescale y

163 pure $ x == xx <?> show { x, xx, y }

167 pure $ x == xx <?> show { x, xx, y }

164

168

165− log "rescaling down then up should be the same as flooring"

169+ log "rescaling down then up should be the same as truncating"

166 quickCheck' 1000 do

170 quickCheck' 1000 do

167 let hi = 20

171 let hi = 20

168 lo <- chooseInt 10 20

172 lo <- chooseInt 10 20

@@ -171,5 +175,5 @@ main = do

171 reifyPrecision hi \hi_ -> do

175 reifyPrecision hi \hi_ -> do

172 x <- genFixedP hi_

176 x <- genFixedP hi_

173 let y = withPrecisionOf lo_ $ rescale x

177 let y = withPrecisionOf lo_ $ rescale x

174− let xx = floorToPrecision lo x

178+ let xx = truncateToPrecision lo x

175 pure $ xx == rescale y <?> show { x, xx, y }

179 pure $ xx == rescale y <?> show { x, xx, y }