Re: [Haskell-cafe] Efficient string construction

On Friday 04 June 2010 00:41:58, Bryan O'Sullivan wrote:

On Thu, Jun 3, 2010 at 9:16 AM, Daniel Fischer wrote:

...

String can be quite memory efficient. As a stupid example,

length (replicate 10000000 'a')

will need less memory than the equivalents using ByteString or Text.

Actually, this will be fused with Data.Text, and should execute more quickly and in less space than String.

Right, forgot about fusion. However, that requires the code to be compiled with optimisations, I think (well, one should never compile ByteString or Text code without). In which case {-# RULES "length/replicate" forall n x. length (replicate n x) = max 0 n #-} would be at least as good as the Data.Text thing ;) Or, to be more fair, if you use Data.List.Stream, it should be fused too and be equally efficient as Data.Text.