rust/src/test/bench/shootout/binarytrees.rs

use std;

import std::_int;

tag tree {
  nil;
  node(@tree, @tree, int);
}

fn item_check(@tree t) -> int {
  alt (*t) {
    case (nil) {
      ret 0;
    }
    case (node(?left, ?right, ?item)) {
      ret item + item_check(left) - item_check(right);
    }
  }
}

fn bottom_up_tree(int item, int depth) -> @tree{
  if (depth > 0) {
    ret @node(bottom_up_tree(2 * item - 1, depth - 1),
              bottom_up_tree(2 * item, depth - 1),
              item);
  } else {
    ret @nil;
  }
}

fn main() {

  auto n = 8;
  auto min_depth = 4;
  auto max_depth;
  if (min_depth + 2 > n) {
    max_depth = min_depth + 2;
  } else {
    max_depth = n;
  }

  auto stretch_depth = max_depth + 1;

  auto stretch_tree = bottom_up_tree(0, stretch_depth);
  log #fmt("stretch tree of depth %d\t check: %d",
           stretch_depth, item_check(stretch_tree));

  auto long_lived_tree = bottom_up_tree(0, max_depth);

  auto depth = min_depth;
  while (depth <= max_depth) {
    auto iterations = _int::pow(2, (max_depth - depth + min_depth) as uint);
    auto chk = 0;

    auto i = 1;
    while (i <= iterations) {
      auto temp_tree = bottom_up_tree(i, depth);
      chk += item_check(temp_tree);

      temp_tree = bottom_up_tree(-i, depth);
      chk += item_check(temp_tree);

      i += 1;
    }

    log #fmt("%d\t trees of depth %d\t check: %d",
             iterations * 2, depth, chk);

    depth += 2;
  }

  log #fmt("long lived trees of depth %d\t check: %d",
           max_depth, item_check(long_lived_tree));
}