On 8 September 2010 10:56, Johan Tibell
The lazy version of Text uses one more word per value than the strict version. This can be significant for small strings (e.g. ~8 characters) where the overhead per character already is quite high. If I counted the size of the BA# constructor correctly, a strict Text has a fixed overhead of 7 words and a lazy Text has an overhead of 8 words. This matters when you e.g. want to use Texts as keys in a Map.
Ah, well if we're playing that game then I have a representation where lazy uses the same storage as strict. :-) The trick is to save a word by using smaller length and offset fields (e.g. 16bit). That can be done for lazy but not strict because with lazy you can always break long strings into multiple 2^16 sized chunks whereas for strict it's essential to be able to use 32/64 bit length/offsets.
Btw, I see that the BA# constructor is not manually unpacked into the Array data type. Is that done automatically since ByteArray# is unlifted or is there some room for improvement here?
I'm not sure what you're referring to here, the definition is: data UArray i e = UArray !i !i !Int ByteArray# The ByteArray# is an unlifted type (but its representation is a pointer to a heap object). Duncan