Re: [Haskell-cafe] Bytestring package: Int and Int64

On Tue, 24 May 2011 10:42:34 +0200, Johan Tibell wrote:

Hi Daniel,

On Tue, May 24, 2011 at 10:07 AM, Daniel Díaz wrote:

...

Hi, cafe,

I just feel curiosity. In the bytestring package, Data.ByteString module, functions like length, index, and others with Int in its type signature, have Int64 in the analogous Data.ByteString.Lazy version. What is the reason?

A strict ByteString is one contiguous chunk of memory so it cannot be longer than an Int (if we assume and Int is either 32 or 64 bits for a second). However, a lazily generated stream can be much bigger than main memory, so it makes sense to use a bigger type to refer to e.g. it length. Now, you might say that lazy ByteString should use Integer instead of Int64. However, Int64 performs much better so I think the loss of generality is worth it.

Johan

Thanks, it makes sense.