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Fix overflows in randomInt #12

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Merged
merged 1 commit into from
Aug 2, 2015
Merged

Fix overflows in randomInt #12

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2 changes: 1 addition & 1 deletion bower.json
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Expand Up @@ -21,7 +21,7 @@
],
"dependencies": {
"purescript-eff": "^0.1.0",
"purescript-integers": "^0.2.0",
"purescript-integers": "^0.2.1",
"purescript-math": "^0.2.0"
}
}
7 changes: 3 additions & 4 deletions src/Control/Monad/Eff/Random.purs
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Expand Up @@ -3,9 +3,7 @@ module Control.Monad.Eff.Random where
import Prelude

import Control.Monad.Eff (Eff())
import Data.Int (fromNumber, toNumber)

import qualified Data.Maybe.Unsafe as U
import Data.Int (fromNumber, toNumber, floor)

-- | The `RANDOM` effect indicates that an Eff action may access or modify the
-- | JavaScript global random number generator, i.e. `Math.random()`.
Expand All @@ -28,7 +26,8 @@ foreign import random :: forall e. Eff (random :: RANDOM | e) Number
randomInt :: forall e. Int -> Int -> Eff (random :: RANDOM | e) Int
randomInt low high = do
n <- random
pure <<< U.fromJust <<< fromNumber <<< Math.floor $ toNumber (high - low + one) * n + toNumber low
let asNumber = (toNumber high - toNumber low + one) * n + toNumber low
return $ floor asNumber

-- | Returns a random number between a minimum value (inclusive) and a maximum
-- | value (exclusive). It is unspecified what happens if `maximum < minimum`.
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