More flexible splitDegrees, but convenient splitDegreesZodiac

src/SwissEphemeris.hs

@@ -60,6 +60,7 @@ module SwissEphemeris
     julianDay,
     deltaTime,
     -- utilities for angles:
+    defaultSplitDegreesOptions,
     splitDegrees,
     splitDegreesZodiac,
   )
@@ -315,27 +316,39 @@ deltaTime jt = do
   return $ realToFrac deltaT
 
 -- | Given a longitude, return the degrees it's from its nearest sign,
--- minutes, seconds and seconds fraction.
+-- minutes, seconds, with seconds rounded. Convenience alias for `splitDegrees`,
+-- when wanting to display e.g. a table in a horoscope.
 splitDegreesZodiac :: Double -> LongitudeComponents
-splitDegreesZodiac d =
-  LongitudeComponents (Just $ toEnum z) deg m s sf
-  where
-    (z, deg, m, s, sf) = splitDegrees' options d
-    options = mkSplitDegOptions $ defaultSplitDegOptions ++ [splitZodiacal]
+splitDegreesZodiac = splitDegrees [SplitZodiacal, RoundSeconds]
 
--- | Given a longitude, return the degrees from zero, minutes, seconds and seconds fraction.
-splitDegrees :: Double -> LongitudeComponents
-splitDegrees d =
-  LongitudeComponents Nothing deg m s sf
+-- | Given a `Double` representing an ecliptic longitude, split it according to any
+-- options from `SplitDegreesOption`:
+-- if `SplitZodiacal` or `SplitNakshatra` are specified, they're returned
+-- in `longitudeZodiacSign` and `longitudeNakshatra`, respectively.
+-- If neither of those is specified, the raw `signum` is then populated, in
+-- `longitudeSignum` (-1 for negative, 1, for positive.)
+-- /NOTE:/ this function can also be used for latitudes, speeds or quantities
+-- from other positional systems (like declinations,) but the zodiacal or
+-- nakshatra components would of course be nonsensical.
+splitDegrees :: [SplitDegreesOption] -> Double -> LongitudeComponents
+splitDegrees options d =
+  LongitudeComponents sign deg m s sf signum' nak
   where
-    (_, deg, m, s, sf) = splitDegrees' options d
-    options = mkSplitDegOptions $ defaultSplitDegOptions
+    (z, deg, m, s, sf) = splitDegrees' flags d
+    flags = foldSplitDegOptions $ map splitOptionToFlag options
+    isZodiacSplit = SplitZodiacal `elem` options
+    isNakshatraSplit = SplitNakshatra `elem` options
+    sign = if isZodiacSplit then (Just . toEnum $ z) else Nothing
+    nak = if isNakshatraSplit then (Just . toEnum $ z) else Nothing
+    signum' = if (not isZodiacSplit && not isNakshatraSplit) then Just z else Nothing
 
 -- | Internal implementation to split a given longitude into components.
 splitDegrees' :: SplitDegFlag -> Double -> (Int, Integer, Integer, Integer, Double)
 splitDegrees' options deg =
   unsafePerformIO $ do
     alloca $ \ideg -> alloca $ \imin -> alloca $ \isec -> alloca $ \dsecfr -> alloca $ \isign -> do
+      -- initialize with 0, since it may never be touched.
+      poke dsecfr 0
       _ <-
         c_swe_split_deg
           (realToFrac deg)

src/SwissEphemeris/Internal.hs

@@ -70,6 +70,30 @@ data ZodiacSignName
   | Pisces
   deriving (Eq, Show, Enum, Generic)
 
+-- | Nakshatras, provided for thoroughness, please excuse the misspellings!
+-- List from: https://en.wikipedia.org/wiki/List_of_Nakshatras
+data NakshatraName
+  = Ashvini
+  deriving (Eq, Show, Enum, Generic)
+
+-- | Options to split a `Double` representing degrees:
+-- RoundSeconds  -- round at the seconds granularity (omits seconds fraction.)
+-- RoundMinutes  -- round at the minutes granularity.
+-- RoundDegrees  -- round at the degrees granularity.
+-- SplitZodiacal -- relative to zodiac signs.
+-- SplitNakshatra -- relative to nakshatra.
+-- KeepSign       -- when rounding, don't round if it'll move it to the next zodiac sector.
+-- KeepDegrees    -- when rounding, don't round if it'll move it to the next degree.
+data SplitDegreesOption
+  = RoundSeconds
+  | RoundMinutes
+  | RoundDegrees
+  | SplitZodiacal
+  | SplitNakshatra
+  | KeepSign
+  | KeepDegrees
+  deriving (Eq, Show, Enum, Generic)
+
 -- | Represents an instant in Julian time.
 -- see:
 -- <https://www.astro.com/swisseph/swephprg.htm#_Toc49847871 8. Date and time conversion functions>
@@ -168,7 +192,9 @@ data LongitudeComponents = LongitudeComponents
     longitudeDegrees :: Integer,
     longitudeMinutes :: Integer,
     longitudeSeconds :: Integer,
-    longitudeSecondsFraction :: Double
+    longitudeSecondsFraction :: Double,
+    longitudeSignum :: Maybe Int,
+    longitudeNakshatra :: Maybe NakshatraName
   }
   deriving (Show, Eq, Generic)
 
@@ -180,14 +206,20 @@ mkCalculationOptions = CalcFlag . foldr ((.|.) . unCalcFlag) 0
 defaultCalculationOptions :: [CalcFlag]
 defaultCalculationOptions = [speed, swissEph]
 
-mkSplitDegOptions :: [SplitDegFlag] -> SplitDegFlag
-mkSplitDegOptions = SplitDegFlag . foldr ((.|.) . unSplitDegFlag) 0
+foldSplitDegOptions :: [SplitDegFlag] -> SplitDegFlag
+foldSplitDegOptions = SplitDegFlag . foldr ((.|.) . unSplitDegFlag) 0
+
+splitOptionToFlag :: SplitDegreesOption -> SplitDegFlag
+splitOptionToFlag RoundSeconds = splitRoundSec
+splitOptionToFlag RoundMinutes = splitRoundMin
+splitOptionToFlag RoundDegrees = splitRoundDeg
+splitOptionToFlag SplitZodiacal = splitZodiacal
+splitOptionToFlag SplitNakshatra = splitNakshatra
+splitOptionToFlag KeepSign = splitKeepSign
+splitOptionToFlag KeepDegrees = splitKeepDeg
 
-defaultSplitDegOptions :: [SplitDegFlag]
-defaultSplitDegOptions =
-  [ splitKeepDeg, -- don't round up to the next degree
-    splitKeepSign -- don't round up to the next sign
-  ]
+defaultSplitDegreesOptions :: [SplitDegreesOption]
+defaultSplitDegreesOptions = [KeepSign, KeepDegrees]
 
 -- Helpers
 

test/SwissEphemerisSpec.hs

@@ -38,13 +38,13 @@ spec = do
   describe "splitDegrees" $ do
     it "splits a given longitude into its components, not relative to the zodiac" $ do
       let longitude = 285.64723120365153
-          split = LongitudeComponents {longitudeZodiacSign = Nothing, longitudeDegrees = 285, longitudeMinutes = 38, longitudeSeconds = 50, longitudeSecondsFraction = 3.233314550481481e-2}
-      (splitDegrees longitude) `shouldBe` split
+          split = LongitudeComponents {longitudeZodiacSign = Nothing, longitudeDegrees = 285, longitudeMinutes = 38, longitudeSeconds = 50, longitudeSecondsFraction = 3.233314550481481e-2, longitudeSignum = Just 1, longitudeNakshatra = Nothing}
+      (splitDegrees defaultSplitDegreesOptions longitude) `shouldBe` split
 
   describe "splitDegreesZodiac" $ do
-    it "splits a given longitude into its components, relative to the nearest zodiac sign" $ do
+    it "splits a given longitude into its components, relative to the nearest zodiac sign; rounds seconds, keeps degrees and sign." $ do
       let longitude = 285.64723120365153
-          split = LongitudeComponents {longitudeZodiacSign = Just Capricorn, longitudeDegrees = 15, longitudeMinutes = 38, longitudeSeconds = 50, longitudeSecondsFraction = 3.233314550481481e-2}
+          split = LongitudeComponents {longitudeZodiacSign = Just Capricorn, longitudeDegrees = 15, longitudeMinutes = 38, longitudeSeconds = 50, longitudeSecondsFraction = 0.0, longitudeSignum = Nothing, longitudeNakshatra = Nothing}
       (splitDegreesZodiac longitude) `shouldBe` split
 
   around_ (withoutEphemerides) $ do