From 579d61d279d5e42d1be117c443b0fb8d131f9645 Mon Sep 17 00:00:00 2001
From: Matthew Leon <ml@matthewleon.com>
Date: Mon, 26 Feb 2018 11:22:31 -0500
Subject: [PATCH] ensure Gen seed is modified after resize

see https://github.com/purescript/purescript-gen/issues/12#issuecomment-368525522
---
 src/Test/QuickCheck/Gen.purs | 15 ++++++---------
 1 file changed, 6 insertions(+), 9 deletions(-)

diff --git a/src/Test/QuickCheck/Gen.purs b/src/Test/QuickCheck/Gen.purs
index 306108d..3a900e1 100644
--- a/src/Test/QuickCheck/Gen.purs
+++ b/src/Test/QuickCheck/Gen.purs
@@ -33,14 +33,13 @@ module Test.QuickCheck.Gen
 import Prelude
 
 import Control.Alt (class Alt)
+import Control.Lazy (class Lazy)
 import Control.Monad.Eff (Eff)
 import Control.Monad.Eff.Random (RANDOM)
+import Control.Monad.Gen.Class (class MonadGen)
 import Control.Monad.Rec.Class (class MonadRec, Step(..), tailRecM)
 import Control.Monad.State (State, runState, evalState)
-import Control.Monad.State.Class (state, get, modify)
-import Control.Monad.Gen.Class (class MonadGen)
-import Control.Lazy (class Lazy)
-
+import Control.Monad.State.Class (modify, state)
 import Data.Array ((!!), length, zip, sortBy)
 import Data.Enum (class BoundedEnum, fromEnum, toEnum)
 import Data.Foldable (fold)
@@ -49,13 +48,10 @@ import Data.List (List(..), toUnfoldable)
 import Data.Maybe (fromMaybe, fromJust)
 import Data.Monoid.Additive (Additive(..))
 import Data.Newtype (unwrap)
-import Data.Tuple (Tuple(..), fst, snd)
 import Data.NonEmpty (NonEmpty, (:|))
-
+import Data.Tuple (Tuple(..), fst, snd)
 import Math ((%))
-
 import Partial.Unsafe (unsafePartial)
-
 import Test.QuickCheck.LCG (Seed, lcgPerturb, lcgN, lcgNext, runSeed, randomSeed)
 
 -- | Tests are parameterized by the `Size` of the randomly-generated data,
@@ -118,7 +114,8 @@ sized f = stateful (\s -> f s.size)
 
 -- | Modify a random generator by setting a new size parameter.
 resize :: forall a. Size -> Gen a -> Gen a
-resize sz g = Gen $ fst <<< runGen g <<< (_ { size = sz }) <$> get
+resize sz g = Gen $ state \{ newSeed, size } ->
+  (_ {size = size} ) <$> runGen g { newSeed, size: sz}
 
 -- | Create a random generator which samples a range of `Number`s i
 -- | with uniform probability.