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

On Fri, Apr 22, 2011 at 11:52:32PM -0700, Tom Brow wrote:

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

According to the haskell report[1] string literals use the overloaded (==) for pattern matching. Matching a numeric, character, or string literal pattern k against a value v succeeds if v == k, where == is overloaded based on the type of the pattern. The match diverges if this test diverges. [1]: http://www.haskell.org/onlinereport/exps.html#sect3.17.2 -- Helgi Kristvin Sigurbjarnarson