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POHaskell Aeson JSON Library ByteString Issue
 

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  1. POHaskell Aeson JSON Library ByteString Issue
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    <p>I'm having trouble finding a function or workaround to convert a <strong>String</strong> to <code>Data.ByteString.Lazy.Internal.ByteString</code></p> <p>One of the functions in the Aeson Json library is <code>decode</code> and has the following description: </p> <pre><code>decode :: FromJSON a =&gt; bytestring-0.10.0.2:Data.ByteString.Lazy.Internal.ByteString -&gt; Maybe a </code></pre> <p>I've tried using the pack function in Data.ByteString.Lazy.Char8 but that returns a different ByteString. Any one know how this can be fixed?</p> <p>The following is the example I'm working on:</p> <pre><code>import Data.Aeson import Data.Text import Control.Applicative import Control.Monad (mzero) import qualified Data.ByteString.Lazy.Internal as BLI import qualified Data.ByteString.Lazy.Char8 as BSL data Person = Person { name :: Text , age :: Int } deriving Show instance FromJSON Person where parseJSON (Object v) = Person &lt;$&gt; v .: (pack "name") &lt;*&gt; v .: (pack "age") parseJSON _ = mzero </code></pre> <p>I tried using <code>decode (BSL.pack "{\"name\":\"Joe\",\"age\":12}") :: Maybe Person</code> and got the following error message:</p> <pre><code>Couldn't match expected type `bytestring-0.10.0.2:Data.ByteString.Lazy.Internal.ByteString' with actual type `BSL.ByteString' In the return type of a call of `BSL.pack' In the first argument of `decode', namely `(BSL.pack "{\"name\":\"Joe\",\"age\":12}")' In the expression: decode (BSL.pack "{\"name\":\"Joe\",\"age\":12}") :: Maybe Person </code></pre> <p>Help!</p>
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    1. USMathanMV
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    1. CODo you have multiple versions of bytestring installed? Try running `ghc-pkg list bytestring` to check.
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    2. COThe list comes up with two items bytestring-0.10.0.2 and bytestring-.10.4.0 - will this cause an issue? I know I had a GHCI linking error earlier when I was playing around with the code above.
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    3. COYes, I had to unregister bytestring-10.4.0 to get it to work.
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      1. USMathanMV
 

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