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#include <stdio.h>
#include <stdbool.h>
#include <stdlib.h>
#include <assert.h>
#include <math.h>
// creates primes.[ch]
int main( int argc, char **argv )
{
int n = 5001; // find all primes up to 5001 by default..
if( argc == 1 )
{
n = 5001;
} else if( argc == 2 )
{
n = atoi( argv[1] );
} else
{
fprintf( stderr, "Usage: mkprimes [MAXVALUE]\n" );
exit(1);
}
int *isprime = (int *) malloc( (n+1) * sizeof(int) );
assert( isprime != NULL );
int i;
for( i=1; i<=n; i++ )
{
isprime[i] = 1; // inititally
}
int upper = (int)(sqrt((double)(n)));
//printf( "debug: n=%d, upper=%d\n", n, upper );
for( i=2; i<=upper; i++ )
{
if( isprime[i] )
{
//printf( "debug: crossing out multiples of %d\n", i );
int j;
for( j=i*i; j<=n; j+=i )
{
isprime[j] = 0;
}
}
}
int np=0;
FILE *out = fopen( "primes.pl", "w" );
assert( out != NULL );
fprintf( out, "# array of all primes <= %d (nb: 1 is not a prime)\n\n", n );
fprintf( out, "my @prime = (" );
for( i=2; i<=n; i++ )
{
if( isprime[i] ) // finally
{
if( np % 10 == 0 )
{
fprintf( out, "\n\t" );
}
fprintf( out, "%d, ", i );
np++;
}
}
fprintf( out, "\n);\n\n" );
fprintf( out, "my $NPRIMES = %d;\n", np );
fclose( out );
}
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