10 May
2011
10 May
'11
4:22 a.m.
On 05/10/11 03:51, Øystein Kolsrud wrote:
Hi! What's the complexity of indexing arrays in Haskell? The Data.Array documentation doesn't seem to mention complexity of any of its functions, and it's not obvious to me how to implement an array data structure with indexing being O(1).
Compilers implement special representation of arrays (an array in memory, rather as you might expect), so indexing is O(1). The price you pay is that array *updates* are O(n) even if you're only changing one element. It has to copy the whole thing in order to leave the original unmodified. (There are also mutable arrays that are more annoyingly imperative to use, Data.Map which has good enough performance for a lot of purposes, etc.)