[Haskell-beginners] When to use ByteString rather than [Char] ...?

[Daniel Fischer]

Am Sonntag 11 April 2010 17:15:22 schrieb Stephen Tetley:
> On 11 April 2010 15:42, Daniel Fischer <daniel.is.fischer at web.de> wrote:
> [SNIP]
>
> > When dealing with short strings, in my experience there are rarely
> > compelling reasons to choose one over the other.
>
> Hi Daniel
>
> Thanks - I was slightly surprised at the results in the paper because
> the 'cons' test for was equal, I thought bytestrings have to do a bit
> more work for a 'cons' - looking at the code lazy bytestring uses one
> constructor and a bit of C memory poking, which is the C memory poking
> more than I'd expect the [Char] version to do.

Well, I guess it depends on what actually happens with fusion (a single 
cons doesn't take significant time for either). If repeated conses lead to 
a chain of one-element chunks, I'd expect that to be significantly slower 
than [Char], but if it's rewritten to

- allocate a new chunk,
- write from end and decrement offset counter,

it shouldn't be slower.

>
> The only 'determinant' I've found for choosing which type for short
> strings is if I'm using a library that forces one or the other on me,

Sure, that's pretty compelling - as long as you don't need two libraries 
with different choices :)

> otherwise I'm swayed by the simplicity of [Char].
>
> Best wishes
>
> Stephen