use std;
import std::arena;
import methods = std::arena::arena;

enum tree/& { nil, node(&tree, &tree, int), }

fn item_check(t: &tree) -> int {
    match *t {
      nil => { return 0; }
      node(left, right, item) => {
        return item + item_check(left) - item_check(right);
      }
    }
}

fn bottom_up_tree(arena: &r/arena::arena,
                  item: int,
                  depth: int) -> &r/tree {
    if depth > 0 {
        return arena.alloc(
            || node(bottom_up_tree(arena, 2 * item - 1, depth - 1),
                    bottom_up_tree(arena, 2 * item, depth - 1),
                    item));
    }
    return arena.alloc(|| nil);
}

fn main(args: ~[~str]) {
    let args = if os::getenv(~"RUST_BENCH").is_some() {
        ~[~"", ~"17"]
    } else if args.len() <= 1u {
        ~[~"", ~"8"]
    } else {
        args
    };

    let n = int::from_str(args[1]).get();
    let min_depth = 4;
    let mut max_depth;
    if min_depth + 2 > n {
        max_depth = min_depth + 2;
    } else {
        max_depth = n;
    }

    let stretch_arena = arena::arena();
    let stretch_depth = max_depth + 1;
    let stretch_tree = bottom_up_tree(&stretch_arena, 0, stretch_depth);

    io::println(fmt!{"stretch tree of depth %d\t check: %d",
                          stretch_depth,
                          item_check(stretch_tree)});

    let long_lived_arena = arena::arena();
    let long_lived_tree = bottom_up_tree(&long_lived_arena, 0, max_depth);
    let mut depth = min_depth;
    while depth <= max_depth {
        let iterations = int::pow(2, (max_depth - depth + min_depth) as uint);
        let mut chk = 0;
        let mut i = 1;
        while i <= iterations {
            let mut temp_tree = bottom_up_tree(&long_lived_arena, i, depth);
            chk += item_check(temp_tree);
            temp_tree = bottom_up_tree(&long_lived_arena, -i, depth);
            chk += item_check(temp_tree);
            i += 1;
        }
        io::println(fmt!{"%d\t trees of depth %d\t check: %d",
                         iterations * 2, depth,
                         chk});
        depth += 2;
    }
    io::println(fmt!{"long lived trees of depth %d\t check: %d",
                     max_depth,
                          item_check(long_lived_tree)});
}