pai.c
#include <stdio.h>
#include <stdlib.h>

int  main(int argc, char* argv[]) 
{
	const float pp = 3.1415926535897932384626433832795028841971693993751058209749445923078164062862089986280348253421170679f;
	float p = pp ;
	long n=4 ;
	if(argc > 1 )
	{
		n=atol( argv[1] ) ;		
	}

	printf("TIMES=%ld\n",n);

	//----
	int  i;
	int seis[n];
	for(i=0; i<n ; i++)
	{
		seis [i] =(int)( p ); //あんま良くないけど
		p -= (float)seis[i] ;
		p = 1.0f / p ;	
//	printf("%d\n",seis[i]);
	}

	long long  bnc = 1.0f ;
	long long  bnb =(long)p ;
	long long  t ;
	printf("bnc=%f\n",p);
	for(i=n-1 ; i >=0 ; i--)
	{	t = bnc ;
		bnc = bnb ;
		bnb = t;
		bnc += seis[i] * bnb  ;
		p = 1.0f / p ;
	}

	printf("%ld / %ld -> %.10f \n",bnc , bnb , (float)(1.0F *bnc/bnb) );
	printf("gosa = %.10f\n",(float)(1.0f*bnc/bnb)-pp);

	return 0;
}
約分プログラムは後で計算する