On Wednesday, 19 March 2014 at 01:29:16 UTC, bearophile wrote:
I think the most commonly useful functions are:
- A lazy range (a simple unbounded segmented Sieve) that
generates primes numbers very quickly, in a given range, or
from 2;
- A isPrime() function. Probably it should cache some of its
computations.
- A function to compute the GCD on ulongs/longs/bigints is
useful.
(Issues 4125 and 7102).
- An efficient and as much as possibly overflow-safe
binomial(n,k) that returns a single number.
I'd also like permutations/combinations/pairwise ranges [Snip]
With such 7 functions/ranges you can do lot of things :-)
Bye,
bearophile
I think we need a solid integer math module more than anything on
this list.
I find myself often reimplementing ilog2, isqrt, isPowerOf2, etc,
etc.
This would be a complement to std.math, std.bitmanip and
core.bitop.
GCD and binomial would fit well in here.
I've recently made use of a prime sieve[1] and something similar
to a pairwise range (triangular range: [0,0],[1,0],[1,1]...)
I think we should be careful about adding an isPrime method, I
think adding an isProbablePrime plus the prime sieve should cover
most use cases.
I agree that combination/pairwise ranges are high on my wishlist,
higher than having GCD/binomial/prime sieve, below having a basic
integer math module.
One important feature of the pairwise range I wrote was slicing
which makes parallelising O(N^2) algorithms much easier.
[1] http://dpaste.dzfl.pl/e91ffe7e4609 Based on the code from
http://create.stephan-brumme.com/eratosthenes/
