Semiprime: Difference between revisions
Rename Perl 6 -> Raku, alphabetize, minor clean-up
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34 semiprimes
</pre>
=={{header|Ada}}==
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yes- 1678 - 2*839
yes- 1679 - 23*73</Pre>
=={{header|AWK}}==
<lang AWK>
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<pre> 4 6 9 10 14 15 21 22 25 26 33 34 35 38 39 46 49 51 55 57 58 62 65 69 74 77 82 85 86 87 91 93 94 95</pre>
=={{header|C
<lang c#>
static void Main(string[] args)
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48 False
49 True
</pre>
=={{header|C++}}==
<lang cpp>
#include <iostream>
bool isSemiPrime( int c )
{
int a = 2, b = 0;
while( b < 3 && c != 1 )
{
if( !( c % a ) )
{ c /= a; b++; }
else a++;
}
return b == 2;
}
int main( int argc, char* argv[] )
{
for( int x = 2; x < 100; x++ )
if( isSemiPrime( x ) )
std::cout << x << " ";
return 0;
}
</lang>
{{out}}
<pre>
4 6 9 10 14 15 21 22 25 26 33 34 35 38 39 46 49 51 55 57 58 62 65 69 74 77 82 85 86 87 91 93 94 95
</pre>
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</pre>
=={{
{{works with|Factor|0.98}}
<lang>USING: kernel math.combinatorics math.primes.factors sequences ;
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</pre>
=={{
<lang forth>: semiprime?
0 swap dup 2 do
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</pre>
=={{
<lang go>package main
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2 == factor($n);
}</lang>
=={{header|Phix}}==
Line 1,745 ⟶ 1,627:
(and (= (length prime-factors) 2)
(= (foldl (λ (x y) (* (car x) y)) 1 prime-factors) n)))))</lang>
=={{header|Raku}}==
(formerly Perl 6)
Here is a naive, grossly inefficient implementation.
<lang perl6>sub is-semiprime (Int $n --> Bool) {
not $n.is-prime and
.is-prime given
$n div first $n %% *, flat grep &is-prime, 2 .. *;
}
use Test;
my @primes = flat grep &is-prime, 2 .. 100;
for ^5 {
nok is-semiprime([*] my @f1 = @primes.roll(1)), ~@f1;
ok is-semiprime([*] my @f2 = @primes.roll(2)), ~@f2;
nok is-semiprime([*] my @f3 = @primes.roll(3)), ~@f3;
nok is-semiprime([*] my @f4 = @primes.roll(4)), ~@f4;
}</lang>
{{out}}
<pre>ok 1 - 17
ok 2 - 47 23
ok 3 - 23 37 41
ok 4 - 53 37 67 47
ok 5 - 5
ok 6 - 73 43
ok 7 - 13 53 71
ok 8 - 7 79 37 71
ok 9 - 41
ok 10 - 71 37
ok 11 - 37 53 43
ok 12 - 3 2 47 67
ok 13 - 17
ok 14 - 41 61
ok 15 - 71 31 79
ok 16 - 97 17 73 17
ok 17 - 61
ok 18 - 73 47
ok 19 - 13 19 5
ok 20 - 37 97 11 31</pre>
===More efficient example===
Here is a more verbose, but MUCH more efficient implementation. Demonstrating using it to find an infinite list of semiprimes and to check a range of integers to find the semiprimes.
{{works with|Rakudo|2017.02}}
<lang perl6>sub is-semiprime ( Int $n where * > 0 ) {
return False if $n.is-prime;
my $factor = find-factor( $n );
return True if $factor.is-prime && ( $n div $factor ).is-prime;
False;
}
sub find-factor ( Int $n, $constant = 1 ) {
my $x = 2;
my $rho = 1;
my $factor = 1;
while $factor == 1 {
$rho *= 2;
my $fixed = $x;
for ^$rho {
$x = ( $x * $x + $constant ) % $n;
$factor = ( $x - $fixed ) gcd $n;
last if 1 < $factor;
}
}
$factor = find-factor( $n, $constant + 1 ) if $n == $factor;
$factor;
}
INIT my $start = now;
# Infinite list of semiprimes
constant @semiprimes = lazy gather for 4 .. * { .take if .&is-semiprime };
# Show the semiprimes < 100
say 'Semiprimes less than 100:';
say @semiprimes[^ @semiprimes.first: * > 100, :k ], "\n";
# Check individual integers, or in this case, a range
my $s = 2⁹⁷ - 1;
say "Is $_ semiprime?: ", .&is-semiprime for $s .. $s + 30;
say 'elapsed seconds: ', now - $start;
</lang>
{{out}}
<pre>Semiprimes less than 100:
(4 6 9 10 14 15 21 22 25 26 33 34 35 38 39 46 49 51 55 57 58 62 65 69 74 77 82 85 86 87 91 93 94 95)
Is 158456325028528675187087900671 semiprime?: True
Is 158456325028528675187087900672 semiprime?: False
Is 158456325028528675187087900673 semiprime?: False
Is 158456325028528675187087900674 semiprime?: False
Is 158456325028528675187087900675 semiprime?: False
Is 158456325028528675187087900676 semiprime?: False
Is 158456325028528675187087900677 semiprime?: False
Is 158456325028528675187087900678 semiprime?: False
Is 158456325028528675187087900679 semiprime?: False
Is 158456325028528675187087900680 semiprime?: False
Is 158456325028528675187087900681 semiprime?: False
Is 158456325028528675187087900682 semiprime?: False
Is 158456325028528675187087900683 semiprime?: False
Is 158456325028528675187087900684 semiprime?: False
Is 158456325028528675187087900685 semiprime?: False
Is 158456325028528675187087900686 semiprime?: False
Is 158456325028528675187087900687 semiprime?: False
Is 158456325028528675187087900688 semiprime?: False
Is 158456325028528675187087900689 semiprime?: False
Is 158456325028528675187087900690 semiprime?: False
Is 158456325028528675187087900691 semiprime?: False
Is 158456325028528675187087900692 semiprime?: False
Is 158456325028528675187087900693 semiprime?: False
Is 158456325028528675187087900694 semiprime?: False
Is 158456325028528675187087900695 semiprime?: False
Is 158456325028528675187087900696 semiprime?: False
Is 158456325028528675187087900697 semiprime?: False
Is 158456325028528675187087900698 semiprime?: False
Is 158456325028528675187087900699 semiprime?: False
Is 158456325028528675187087900700 semiprime?: False
Is 158456325028528675187087900701 semiprime?: True
elapsed seconds: 0.0574433</pre>
=={{header|REXX}}==
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