旋转木马の阶梯

/*
 * Convert a string to an integer.
 */
 
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
 
%%{
	machine atoi;
	write data;
}%%
 
long long atoi( char *str )
{
	char *p = str, *pe = str + strlen( str );
	int cs;
	long long val = 0;
	bool neg = false;
 
	%%{
		action see_neg {
			neg = true;
		}
 
		action add_digit {
			val = val * 10 + (fc - '0');
		}
 
		main :=
			( '-'@see_neg | '+' )? ( digit @add_digit )+
			'\n';
 
		# Initialize and execute.
		write init;
		write exec;
	}%%
 
	if ( neg )
		val = -1 * val;
 
	if ( cs &lt; atoi_first_final )
		fprintf( stderr, "atoi: there was an error\n" );
 
	return val;
};
 
#define BUFSIZE 1024
 
int main()
{
	char buf[BUFSIZE];
	while ( fgets( buf, sizeof(buf), stdin ) != 0 ) {
		long long value = atoi( buf );
		printf( "%lld\n", value );
	}
	return 0;
}