[Haskell-cafe] Pattern matching on lazy bytestrings: how does it work?

[Tom Brow]

I noticed today that I can pattern match against lazy bytestrings when using
the OverloadedStrings extension:

import Data.ByteString.Char8 ()
>
> import Data.ByteString.Lazy.Char8
>
>
>> f :: ByteString -> Bool
>
> f "abc" = True
>
> f _ = False
>
>
>> main = do
>
> print $ f $ fromChunks ["abc"]
>
> print $ f $ fromChunks ["a","bc"]
>
>
When I run the above, I get:

True
>
> True
>
>
Given that pattern matching is based on data constructors, how is it
possible that (Chunk "abc Empty) and (Chunk "a" (Chunk "bc" Empty)) match
the same pattern?

Tom
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