Computing Pi with C

Here's the code:

/<><><><><><><><><><><><><><><><><><><><><><><>/

/<> Compute Pi to arbitrary precision <><><><>/

/<> uses Machin's formula... <><><><><><><><>/

/<> pi/4 = 4 arctan (1/5) - arctan (1/239)<>/

/<> Calculates Pi to 10 decimal places <><>/

/<><><><><><><><><><><><><><><><><><><><><>/

#include <stdio.h>

#define BASE 10000

int nblock;

int *tot;

int *t1;

int *t2;

int *t3;

main(argc, argv)

int argc;

char **argv;

{

int ndigit = 10;

if(argc == 2)

ndigit = atoi(argv[1]);

else {

fprintf(stderr, "Usage: %s ndigit\n", argv[0]);

fprintf(stderr, "(Assuming 10 digits)\n");

}

if(ndigit < 20) ndigit = 20;

nblock = ndigit/4;

tot = (int *)malloc(nblock*sizeof(int));

t1 = (int *)malloc(nblock*sizeof(int));

t2 = (int *)malloc(nblock*sizeof(int));

t3 = (int *)malloc(nblock*sizeof(int));

if(!tot || !t1 || !t2 || !t3){

fprintf(stderr, "Not enough memory\n");

exit(1);

}

arctan(tot, t1, t2, 5, 1);

mult(tot, 4);

arctan(t3, t1, t2, 239, 2);

sub(tot, t3);

mult(tot, 4);

print(tot);

}

arctan(result, w1, w2, denom, onestep)

int *result, *w1, *w2, denom, onestep;

{

int denom2 = denom*denom;

int k = 1;

set(result, 1);

div(result, denom);

copy(w1, result);

do{

if(onestep)

div(w1, denom2);

else {

div(w1, denom);

div(w1, denom);

}

copy(w2, w1);

div(w2, 2*k+1);

if(k%2)

sub(result, w2);

else

add(result, w2);

k++;

} while(!zero(w2));

}

copy(result, from)

int *result, *from;

{

int i;

for(i=0; i<nblock; i++)

result[i] = from[i];

}

zero(result)

int *result;

{

int i;

for(i=0;i<nblock; i++)

if(result[i])

return 0;

return 1;

}

add(result, increm)

int *result, *increm;

{

int i;

for(i=nblock-1; i>=0; i--){

result[i] += increm[i];

if(result[i] >= BASE){

result[i] -= BASE;

result[i-1]++;

}

}

}

sub(result, decrem)

int *result, *decrem;

{

int i;

for(i=nblock-1; i>=0; i--){

result[i] -= decrem[i];

if(result[i] < 0){

result[i] += BASE;

result[i-1]--;

}

}

}

mult(result, factor)

int *result, factor;

{

int i, carry = 0;

for(i=nblock-1; i>=0; i--){

result[i] *= factor;

result[i]+= carry; carry = result[i]/BASE;

result[i] %= BASE;

}

}

div(result, denom)

int *result, denom;

{

int i,carry = 0;

for(i=0; i<nblock; i++){

result[i] += carry*BASE;

carry = result[i] % denom;

result[i] /= denom;

}

}

set(result, rhs)

int *result, rhs;

{

int i;

for(i=0; i<nblock; i++)

result[i] = 0;

result[0] = rhs;

}

print(result)

int *result;

{

int i, k;

char s[10];

printf("%1d.\n", result[0]);

for(i=1; i<nblock; i++){

sprintf(s, "%4d ", result[i]);

for(k=0; k<5; k++)

if(s[k] == ' ') s[k] = '0';

printf("%c%c%c%c", s[0], s[1], s[2], s[3]);

if(i%15 == 0) printf("\n");

}

printf("\n");

}

/<><><><><><><><><>/

/<> End of Prog<><>/

/<><><><><><><><></

/Pi= 3.1415926535