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// The Computer Language Benchmarks Game
// http://benchmarksgame.alioth.debian.org/
//
// contributed by the Rust Project Developers
// Copyright (c) 2013-2014 The Rust Project Developers
//
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions
// are met:
//
// - Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
//
// - Redistributions in binary form must reproduce the above copyright
// notice, this list of conditions and the following disclaimer in
// the documentation and/or other materials provided with the
// distribution.
//
// - Neither the name of "The Computer Language Benchmarks Game" nor
// the name of "The Computer Language Shootout Benchmarks" nor the
// names of its contributors may be used to endorse or promote
// products derived from this software without specific prior
// written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
// FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
// COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
// INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
// (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
// SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
// HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
// STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
// ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
// OF THE POSSIBILITY OF SUCH DAMAGE.
use std::io;
use std::str::FromStr;
use num_bigint::BigInt;
use num_integer::Integer;
use num_traits::{FromPrimitive, One, ToPrimitive, Zero};
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_i32(i: i32) -> BigInt {
FromPrimitive::from_i32(i).unwrap()
}
fn extract_digit(&self) -> i32 {
if self.numer > self.accum {
return -1;
}
let (q, r) = (&self.numer * Context::from_i32(3) + &self.accum).div_rem(&self.denom);
if r + &self.numer >= self.denom {
return -1;
}
q.to_i32().unwrap()
}
fn next_term(&mut self, k: i32) {
let y2 = Context::from_i32(k * 2 + 1);
self.accum = (&self.accum + (&self.numer << 1)) * &y2;
self.numer = &self.numer * Context::from_i32(k);
self.denom = &self.denom * y2;
}
fn eliminate_digit(&mut self, d: i32) {
let d = Context::from_i32(d);
let ten = Context::from_i32(10);
self.accum = (&self.accum - &self.denom * d) * &ten;
self.numer = &self.numer * ten;
}
}
fn pidigits(n: isize, out: &mut dyn io::Write) -> io::Result<()> {
let mut k = 0;
let mut context = Context::new();
for i in 1..=n {
let mut d;
loop {
k += 1;
context.next_term(k);
d = context.extract_digit();
if d != -1 {
break;
}
}
write!(out, "{}", d)?;
if i % 10 == 0 {
writeln!(out, "\t:{}", i)?;
}
context.eliminate_digit(d);
}
let m = n % 10;
if m != 0 {
for _ in m..10 {
write!(out, " ")?;
}
writeln!(out, "\t:{}", n)?;
}
Ok(())
}
const DEFAULT_DIGITS: isize = 512;
fn main() {
let args = std::env::args().collect::<Vec<_>>();
let n = if args.len() < 2 {
DEFAULT_DIGITS
} else if args[1] == "--bench" {
return pidigits(DEFAULT_DIGITS, &mut std::io::sink()).unwrap();
} else {
FromStr::from_str(&args[1]).unwrap()
};
pidigits(n, &mut std::io::stdout()).unwrap();
}
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