[ZPT] Re: re# IMPORTANT NOTE## Getting the length of a BTree, TreeSet,or output of keys,# values, or items of same is expensive. If you needto get the# length, you need to maintain this separately.#Pleasemake "total" lazy!

[Casey Duncan]

ZCatalog results can be just as bad. Doing a len on a Lazy sequence can 
sometimes result in touching every item.

Just make total a method.

Also, why are you calling this total? I think that name implies an 
aggregate sum, not a length. Perhaps it should be called 
"sequence-length" 8*)

-Casey

Chris Withers wrote:
> Steve Alexander wrote:
> 
>># IMPORTANT NOTE
>>#
>># Getting the length of a BTree, TreeSet, or output of keys,
>># values, or items of same is expensive. If you need to get the
>># length, you need to maintain this separately.
>>
> 
> But why would the length of a ZCatalog results set need to be calculated in this way?
> 
> cheers,
> 
> Chris
> 
> PS: If it does need to calculate it in this way, I think that's a bug in the BTrees
> implementation. The users shouldn't have to care about how the length is stored or
> computed, the BTrees internally should keep a seperate counter ifthat's what they need to
> do, then it can be kept in synch in a much tigher loop..
> 
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