Prime numbers whose neighboring pairs are tetraprimes: Difference between revisions

=={{header|Raku}}==

{{trans|Wren}}

<syntaxhighlight lang="raku" line># 20230721 Raku programming solution

my @primes = (2..1e7).grep: *.is-prime; # cannot do lazy here

sub median { # based on https://rosettacode.org/wiki/Averages/Median#Raku

return { ( .[(*-1) div 2] + .[* div 2] ) / 2 }(@_) # for already sorted

}

sub isTetraPrime ($n is copy) { # is cached {

my ($count,$prevFact) = 0, 1;

for @primes -> \p {

my $limit = p * p;

if $count == 0 {

$limit = $limit * $limit

} elsif $count == 1 {

$limit *= p

}

if $limit <= $n {

while $n %% p {

return False if ( $count == 4 or p == $prevFact );

$count++;

$n div= p;

$prevFact = p

}

} else {

last

}

}

if $n > 1 {

return False if ( $count == 4 or $n == $prevFact );

$count++

}

return $count == 4

}

my ( $j, @tetras1, @tetras2, $sevens1, $sevens2 ) = 1e5;

my \highest7 = @primes.[*-1];

my \highest6 = @primes.first: * < 1e6, :end;

my \highest5 = @primes.first: * < 1e5, :end;

for @primes -> \p {

if isTetraPrime p-1 and isTetraPrime p-2 {

@tetras1.push: p;

$sevens1++ if ( (p-1) %% 7 or (p-2) %% 7 );

}

if isTetraPrime p+1 and isTetraPrime p+2 {

@tetras2.push: p;

$sevens2++ if ( (p+1) %% 7 or (p+2) %% 7 );

}

if p == highest5 | highest6 | highest7 {

for 0,1 -> \i {

my (\sevens, \t, @tetras) := i == 0

?? ( $sevens1, "preceding", @tetras1 )

!! ( $sevens2, "following", @tetras2 );

my \c = @tetras.elems;

say "Found {c} primes under $j whose {t} neighboring pair are tetraprimes:";

if p == highest5 {

say [~] $_>>.fmt('%6s') for @tetras.rotor(10,:partial);

}

say "of which {sevens} have a neighboring pair one of whose factors is 7.\n";

my \gaps = ( @tetras[^c].rotor(2=>-1).map: { ( [-] $_ ).abs } ).sort;

my (\Min,\Max,\Med) = gaps[0], gaps[*-1], median(gaps);

say "Minimum gap between those {c} primes : {Min}";

say "Median gap between those {c} primes : {Med}";

say "Maximum gap between those {c} primes : {Max}";

say()

}

$j *= 10

}

}</syntaxhighlight>

{{out}} Same as Wren