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// Copyright 2013 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
extern mod extra;
use std::from_str::FromStr;
use std::num::One;
use std::num::Zero;
use std::num::FromPrimitive;
use extra::bigint::BigInt;
struct Context {
numer: BigInt,
accum: BigInt,
denom: BigInt,
}
impl Context {
fn new() -> Context {
Context {
numer: One::one(),
accum: Zero::zero(),
denom: One::one(),
}
}
fn from_int(i: int) -> BigInt {
FromPrimitive::from_int(i).unwrap()
}
fn extract_digit(&self) -> int {
if self.numer > self.accum {return -1;}
let (q, r) =
(self.numer * Context::from_int(3) + self.accum)
.div_rem(&self.denom);
if r + self.numer >= self.denom {return -1;}
q.to_int().unwrap()
}
fn next_term(&mut self, k: int) {
let y2 = Context::from_int(k * 2 + 1);
self.accum = (self.accum + (self.numer << 1)) * y2;
self.numer = self.numer * Context::from_int(k);
self.denom = self.denom * y2;
}
fn eliminate_digit(&mut self, d: int) {
let d = Context::from_int(d);
let ten = Context::from_int(10);
self.accum = (self.accum - self.denom * d) * ten;
self.numer = self.numer * ten;
}
}
fn pidigits(n: int) {
let mut k = 0;
let mut context = Context::new();
for i in range(1, n + 1) {
let mut d;
loop {
k += 1;
context.next_term(k);
d = context.extract_digit();
if d != -1 {break;}
}
print!("{}", d);
if i % 10 == 0 {print!("\t:{}\n", i);}
context.eliminate_digit(d);
}
let m = n % 10;
if m != 0 {
for _ in range(m, 10) {print(" ");}
print!("\t:{}\n", n);
}
}
fn main() {
let args = std::os::args();
let n = if args.len() < 2 {
512
} else {
FromStr::from_str(args[1]).unwrap()
};
pidigits(n);
}
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