NAME

SYNTAX

void primegen_init(&pg);
uint64 primegen_next(&pg);
uint64 primegen_peek(&pg);
uint64 primegen_count(&pg,bound);
void primegen_skipto(&pg,bound);

struct primegen pg;
uint64 bound;

DESCRIPTION

The simplest way to use primegen is to call primegen_init and then call primegen_next repeatedly. The first call to primegen_next will return 2; the next call will return 3; the next call will return 5; and so on.

At each moment the next few primes to be returned by primegen_next are buffered inside pg. primegen_init initializes pg with the first few primes, starting at 2. You must initialize pg with primegen_init before using pg with any of the other primegen routines. You may call primegen_init again to start over at 2.

primegen_next returns the next buffered prime and removes that prime from pg. primegen_peek returns the next buffered prime but does not change pg.

primegen_skipto discards all primes up to bound. It has the same effect as

     while (primegen_peek(&pg) < bound)
       primegen_next(&pg);

primegen_count discards all primes up to bound and returns the number of primes discarded.

You can set up several independent generators; all primegen data is stored in pg. Beware, however, that each struct primegen uses quite a bit of memory.

SEE ALSO