Double factorial and primorial

[bodrato at mail.dm.unipi.it]

Il Mer, 21 Dicembre 2011 10:56 am, Niels Möller ha scritto:
> The simplest and *general* interface I can come up with takes a range as

A range delimited by? two unsigned long?
To be *general* we should allow two mpzs... but it looks too hard to
implement.

> input, and a callback function. And then that callback function is
> invoked for each prime in the interval. Could perhaps also return the

And whenever the callback returns a non-zero, the loop is interrupted, so
that one can stop when the needed prime is found.

> number of primes in the interval, and allow a NULL callback.

If the loop can be interrupted, it is probably better to return the last
used prime (or zero if there are none in the range).

The prime counting function can have its own interface and its specialised
code: with a bitwise sieve, popcount is faster than some kind of loop.

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