import std.c.stdio;import std.c.stdlib;import std.c.time;const int LONG_TIME=4000;byte[] p;byte[] t;int q;int main(char[][] args){	int startime, endtime;	int i;	if (args.length == 2) {		sscanf(&args[1][0],"%d",&q);	} else {		printf("Usage: pi [precision]\n");		exit(55);	}	if (q < 0)	{		printf("Precision was too low, running with precision of 0.\n");		q = 0;	}	if (q > LONG_TIME)	{	    printf("Be prepared to wait a while...\n");	}	// Compute one more digit than we display to compensate for rounding	q++;	p.length = q + 1;	t.length = q + 1;	/* compute pi */	std.c.time.time(&startime);	arctan(2);	arctan(3);	mul4();	std.c.time.time(&endtime);	// Return to the number of digits we want to display	q--;	/* print pi */	printf("pi = %d.",cast(int)(p[0]));	for (i = 1; i <= q; i++)	printf("%d",cast(int)(p));	printf("\n");	printf("%ld seconds to compute pi with a precision of %d digits.\n",endtime-startime,q);	return 0;}void arctan(int s){	int n;	t[0] = 1;	div(s); /* t[] = 1/s */	add();	n = 1;	do {		mul(n);		div(s * s);		div(n += 2);		if (((n-1) / 2) % 2 == 0)			add();		else			sub();	} while (!tiszero());}void add(){	int j;	for (j = q; j >= 0; j--)	{		if (t[j] + p[j] > 9) {			p[j] += t[j] - 10;			p[j-1] += 1;		} else			p[j] += t[j];	}}void sub(){	int j;	for (j = q; j >= 0; j--)		if (p[j] < t[j]) {			p[j] -= t[j] - 10;			p[j-1] -= 1;		} else			p[j] -= t[j];}void mul(int multiplier){	int b;	int i;	int carry = 0, digit = 0;	for (i = q; i >= 0; i--) {		b = (t * multiplier + carry);		carry = b / 10;		digit = b - carry * 10;		t = digit;	}}/* t[] /= l */void div(int divisor){	int i, b;	int quotient, remainder = 0;	for (i = 0; i <= q; i++) {		b = (10 * remainder + t);		quotient = b / divisor;		remainder = b - divisor * quotient;		t = quotient;	}}void div4(){	int i, c, d = 0;	for (i = 0; i <= q; i++) {		c = (10 * d + p) / 4;		d = (10 * d + p) % 4;		p = c;	}}void mul4(){	int i, c, d;	d = c = 0;	for (i = q; i >= 0; i--) {		d = (p * 4 + c) % 10;		c = (p * 4 + c) / 10;		p = d;	}}int tiszero(){	int k;	for (k = 0; k <= q; k++)		if (t[k] != 0)			return false;	return true;}

let main args =  let q =    if Array.length args = 2    then int_of_string args.(1) + 1    else 101  in  let p = Array.make (q + 1) 0  and t = Array.make (q + 1) 0  in  let add () =    for j = q downto 0 do      if t.(j) + p.(j) > 9      then	(	 p.(j) <- p.(j) + t.(j) - 10;	 p.(j-1) <- p.(j-1) + 1	)      else	p.(j) <- p.(j) + t.(j)    done  and sub () =    for j = q downto 0 do      if p.(j) < t.(j)      then	(	 p.(j) <- p.(j) - t.(j) + 10;	 p.(j - 1) <- p.(j - 1) - 1	)      else	p.(j) <- p.(j) - t.(j)    done  and mul multiplier =    let carry = ref 0    and digit = ref 0    and b = ref 0    in    for i = q downto 0 do      b := t.(i) * multiplier + !carry;      digit := !b mod 10;      carry := !b / 10;      t.(i) <- !digit    done  and div divisor =    let quotient = ref 0    and remainder = ref 0    and b = ref 0    in    for i = 0 to q do      b := 10 * !remainder + t.(i);      quotient := !b / divisor;      remainder := !b mod divisor;      t.(i) <- !quotient    done  and mul4 () =    let c = ref 0    and d = ref 0    in    for i = q downto 0 do      d := (p.(i) * 4 + !c) mod 10;      c := (p.(i) * 4 + !c) / 10;      p.(i) <- !d    done  and tiszero () =    let k = ref 0    and r = ref true    in    while (!k <= q) && !r do      r := t.(!k) = 0;      k := !k + 1    done;    !r  in  let arctan s =    let n = ref 1    in    let loop () =      mul !n;      div (s * s);      n := !n + 2;      div !n;      if ((!n - 1) / 2) mod 2 = 0      then add ()      else sub ()    in    t.(0) <- 1;    div s;    add ();    loop ();    while not (tiszero ()) do      loop ()    done  in  let show array =    Array.iter print_int array  and run () =    arctan 2;    arctan 3;    mul4 ()  in  let time () =    let before = Sys.time ()    in    run ();    let after = Sys.time ()    in    show p;    print_newline();    Printf.printf "Time measured: %f" (after -. before)  in  Printf.printf "Computing pi (%d digits)..." (q - 1);  time ();;main Sys.argv;;