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|
CREATE SCHEMA IF NOT EXISTS pwc155;
/*
testdb=> select pwc155.fortunate( 8 ) order by 1;
fortunate
-----------
3
5
7
13
17
19
23
37
(8 rows)
*/
CREATE OR REPLACE FUNCTION
pwc155.fortunate( int )
RETURNS SETOF integer
AS $CODE$
# a subroutine to see if a number
# is prime
my $is_prime = sub {
return 1 if $_[0] == 1;
return 1 if $_[0] == 2;
for my $i ( 2 .. $_[0] - 1 ) {
return 0 if $_[0] % $i == 0;
}
return 1;
};
# generates the first n primes
my $generate_primes = sub {
my @primes;
for my $p ( 2 .. 99999 ) {
push @primes, $p if $is_prime->( $p );
return @primes if @primes == $_[0];
}
};
my $max = sub {
my $max = 0;
for (@_) {
$max = $_ if $_ > $max;
}
elog( DEBUG, "MAX = $max in " . join( ',', @_ ) );
return $max;
};
my $pn = sub {
my $result = 1;
for ( @_ ) {
$result *= $_;
}
return $result;
};
my $limit = $_[0] || 8;
my %unique;
for my $n ( 1 .. 999999 ) {
# generate the first n primes
my @primes = $generate_primes->( $n );
my $start = $max->( @primes ) + 1;
elog( DEBUG, "Primes = " . join( ',', @primes ) . " with max = $start" );
for my $m ( $start .. 999999 ) {
my $fortunate = $pn->( @primes ) + $m;
elog( DEBUG, "Computing $m -> " . $pn->( @primes ) . " + $m = $fortunate = " . $is_prime->( $fortunate ) );
next if ! $is_prime->( $fortunate );
$unique{ $m }++;
next if $unique{ $m } > 1;
return_next( $m );
last;
}
$limit--;
last if $limit <= 0;
}
return undef;
$CODE$
LANGUAGE plperl;
|
