divRem by `-' performance
Albert Y. C. Lai
trebla at vex.net
Thu Oct 18 19:54:45 CEST 2012
On 12-10-18 05:24 AM, Serge D. Mechveliani wrote:
> And concerning this example: I am not even sure now that it worths to
> setting $! there.
> Because I deliberately program qRem as returning a pair (quot, rem),
> and do not program a separate function for rem. And to obtain rem,
> one applies snd (qRem n m), and due to laziness, quot does not
> spend the cost. I do not know, may be, using $! may damage this style.
snd (quot, rem) does not spend the arithmetic cost of quot, but spends
the memory cost of quot. Memory cost is not just occupation of memory,
but also writing of memory and computing of addresses, which is not
exactly cheaper than arithmetic.
More information about the Glasgow-haskell-users