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/*
* TASK #1 - Prime Palindrome
*
* GUEST LANGUAGE: THIS IS THE C VERSION OF ch-1.pl.
*/
#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#include <string.h>
#include <assert.h>
#include <unistd.h>
#include <ctype.h>
#include "primes.h"
bool debug=false;
// int n = process_singlearg( argc, argv );
// Process the -d flag, and check that there is a single
// remaining argument, return it's numeric value.
int process_singlearg( int argc, char **argv )
{
int arg=1;
if( argc>1 && strcmp( argv[arg], "-d" ) == 0 )
{
debug = true;
arg++;
}
int left = argc-arg;
if( left != 1 )
{
fprintf( stderr,
"Usage: prime-palindrome [-d] firstN\n" );
exit(1);
}
// element is in argv[arg]
if( debug )
{
printf( "debug: remaining argument is in arg=%d, firstn=%s\n",
arg, argv[arg] );
}
return atoi( argv[arg] );
}
/*
* bool ispal = ispalindrome( x );
* Return 1 iff $x is palindromic in base 10, otherwise 0.
*/
bool ispalindrome( int x )
{
char str[20];
sprintf( str, "%d", x );
int len = strlen(str);
for( int i=0; i<len/2; i++ )
{
if( str[i] != str[len-1-i] )
{
return 0;
}
}
return 1;
}
int main( int argc, char **argv )
{
int firstn = process_singlearg( argc, argv );
int *primes = primes_upto( firstn );
//bool ispal = ispalindrome( firstn );
//printf( "ispal(%d)? %d\n", firstn, (int)ispal );
printf( "Palindromic primes up to %d\n", firstn );
for( int i=0; primes[i] > 0; i++ )
{
if( ispalindrome( primes[i] ) )
{
printf( "%d\n", primes[i] );
}
}
free( primes );
return 0;
}
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