Writing infinite list to skip every factor of p?
How can I efficiently represent the list [0..] \\ [t+0*p, t+1*p ..]?
I have defined:
Prelude> let factors p t = [t+0*p, t+1*p ..]
I want to efficiently represent an infinite list that is the difference of
[0..] and factors p t, but using \\ from Data.List requires too much
memory for even medium-sized lists:
Prelude Data.List> [0..10000] \\ (factors 5 0)
<interactive>: out of memory
I know that I can represent the values between t+0*p and t+1*p with:
Prelude> let innerList p1 p2 t = [t+p1+1, t+p1+2 .. t+p2-1]
Prelude> innerList 0 5 0
[1,2,3,4]
However, repeatedly calculating and concatenating innerList for increasing
intervals seems clumsy.
Can I efficiently represent [0..] \\ (factors p t) without calculating rem
or mod for each element?
No comments:
Post a Comment