Allow full Number range for chooseFloat (#97)

Author: jacereda

src/Test/QuickCheck/Gen.purs

@@ -122,9 +122,11 @@ resize sz g = Gen $ state \{ newSeed, size } ->
 -- | Create a random generator which samples a range of `Number`s i
 -- | with uniform probability.
 choose :: Number -> Number -> Gen Number
-choose a b = (*) (max' - min') >>> (+) min' <$> uniform where
-  min' = min a b
-  max' = max a b
+choose a b = (*) (max' - min') >>> (+) min' >>> unscale <$> uniform where
+  unscale = (_ * 2.0)
+  scale = (_ * 0.5)
+  min' = scale $ min a b
+  max' = scale $ max a b
 
 -- | Create a random generator which chooses uniformly distributed
 -- | integers from the closed interval `[a, b]`.

test/Main.purs

@@ -2,22 +2,24 @@ module Test.Main where
 
 import Prelude
 
-import Effect (Effect)
-import Effect.Console (log, logShow)
-import Effect.Exception (try)
 import Control.Monad.Gen.Class as MGen
+import Data.Array (all)
 import Data.Array.Partial (head)
 import Data.Either (isLeft)
 import Data.Foldable (sum)
 import Data.Generic.Rep (class Generic)
 import Data.Generic.Rep.Show (genericShow)
 import Data.Tuple (fst)
+import Effect (Effect)
+import Effect.Console (log, logShow)
+import Effect.Exception (try)
+import Global (isFinite)
 import Partial.Unsafe (unsafePartial)
+import Random.LCG (mkSeed)
 import Test.Assert (assert)
 import Test.QuickCheck (class Testable, quickCheck, (/=?), (<=?), (<?), (==?), (>=?), (>?))
 import Test.QuickCheck.Arbitrary (arbitrary, genericArbitrary, class Arbitrary)
-import Test.QuickCheck.Gen (Gen, vectorOf, randomSample', resize, Size, runGen, sized)
-import Random.LCG (mkSeed)
+import Test.QuickCheck.Gen (Gen, Size, randomSample, randomSample', resize, runGen, sized, vectorOf)
 
 data Foo a = F0 a | F1 a a | F2 { foo :: a, bar :: Array a }
 derive instance genericFoo :: Generic (Foo a) _
@@ -84,6 +86,9 @@ main = do
   quickCheck     $ 4 >?  3
   quickCheckFail $ 4 <=? 3
 
+  log "Checking that chooseFloat over the whole Number range always yields a finite value"
+  randomSample (MGen.chooseFloat ((-1.7976931348623157e+308)) (1.7976931348623157e+308)) >>= assert <<< all isFinite
+
   where
   go n = map (sum <<< unsafeHead) $ randomSample' 1 (vectorOf n (arbitrary :: Gen Int))