type T = uint;

#[doc = "
Divide two numbers, return the result, rounded up.

# Arguments

* x - an integer
* y - an integer distinct from 0u

# Return value

The smallest integer `q` such that `x/y <= q`.
"]
pure fn div_ceil(x: uint, y: uint) -> uint {
    let div = div(x, y);
    if x % y == 0u { ret div;}
    else { ret div + 1u; }
}

#[doc = "
Divide two numbers, return the result, rounded to the closest integer.

# Arguments

* x - an integer
* y - an integer distinct from 0u

# Return value

The integer `q` closest to `x/y`.
"]
pure fn div_round(x: uint, y: uint) -> uint {
    let div = div(x, y);
    if x % y * 2u  < y { ret div;}
    else { ret div + 1u; }
}

#[doc = "
Divide two numbers, return the result, rounded down.

Note: This is the same function as `div`.

# Arguments

* x - an integer
* y - an integer distinct from 0u

# Return value

The smallest integer `q` such that `x/y <= q`. This
is either `x/y` or `x/y + 1`.
"]
pure fn div_floor(x: uint, y: uint) -> uint { ret x / y; }

#[doc = "Produce a uint suitable for use in a hash table"]
pure fn hash(x: uint) -> uint { ret x; }

#[doc = "
Iterate over the range [`lo`..`hi`), or stop when requested

# Arguments

* lo - The integer at which to start the loop (included)
* hi - The integer at which to stop the loop (excluded)
* it - A block to execute with each consecutive integer of the range.
       Return `true` to continue, `false` to stop.

# Return value

`true` If execution proceeded correctly, `false` if it was interrupted,
that is if `it` returned `false` at any point.
"]
fn iterate(lo: uint, hi: uint, it: fn(uint) -> bool) -> bool {
    let mut i = lo;
    while i < hi {
        if (!it(i)) { ret false; }
        i += 1u;
    }
    ret true;
}

#[doc = "Returns the smallest power of 2 greater than or equal to `n`"]
fn next_power_of_two(n: uint) -> uint {
    let halfbits: uint = sys::size_of::<uint>() * 4u;
    let mut tmp: uint = n - 1u;
    let mut shift: uint = 1u;
    while shift <= halfbits { tmp |= tmp >> shift; shift <<= 1u; }
    ret tmp + 1u;
}

#[doc = "
Parse a buffer of bytes

# Arguments

* buf - A byte buffer
* radix - The base of the number

# Failure

`buf` must not be empty
"]
fn parse_buf(buf: [u8], radix: uint) -> option<uint> {
    if vec::len(buf) == 0u { ret none; }
    let mut i = vec::len(buf) - 1u;
    let mut power = 1u;
    let mut n = 0u;
    loop {
        alt char::to_digit(buf[i] as char, radix) {
          some(d) { n += d * power; }
          none { ret none; }
        }
        power *= radix;
        if i == 0u { ret some(n); }
        i -= 1u;
    };
}

#[doc = "Parse a string to an int"]
fn from_str(s: str) -> option<uint> { parse_buf(str::bytes(s), 10u) }

#[doc = "Convert to a string in a given base"]
fn to_str(num: uint, radix: uint) -> str {
    let mut n = num;
    assert (0u < radix && radix <= 16u);
    fn digit(n: uint) -> char {
        ret alt n {
              0u { '0' }
              1u { '1' }
              2u { '2' }
              3u { '3' }
              4u { '4' }
              5u { '5' }
              6u { '6' }
              7u { '7' }
              8u { '8' }
              9u { '9' }
              10u { 'a' }
              11u { 'b' }
              12u { 'c' }
              13u { 'd' }
              14u { 'e' }
              15u { 'f' }
              _ { fail }
            };
    }
    if n == 0u { ret "0"; }
    let mut s: str = "";
    while n != 0u {
        s += str::from_byte(digit(n % radix) as u8);
        n /= radix;
    }
    let mut s1: str = "";
    let mut len: uint = str::len(s);
    while len != 0u { len -= 1u; s1 += str::from_byte(s[len]); }
    ret s1;
}

#[doc = "Convert to a string"]
fn str(i: uint) -> str { ret to_str(i, 10u); }

#[test]
fn test_from_str() {
    assert uint::from_str("0") == some(0u);
    assert uint::from_str("3") == some(3u);
    assert uint::from_str("10") == some(10u);
    assert uint::from_str("123456789") == some(123456789u);
    assert uint::from_str("00100") == some(100u);

    assert uint::from_str("") == none;
    assert uint::from_str(" ") == none;
    assert uint::from_str("x") == none;
}

#[Test]
fn test_parse_buf() {
    import str::bytes;
    assert uint::parse_buf(bytes("123"), 10u) == some(123u);
    assert uint::parse_buf(bytes("1001"), 2u) == some(9u);
    assert uint::parse_buf(bytes("123"), 8u) == some(83u);
    assert uint::parse_buf(bytes("123"), 16u) == some(291u);
    assert uint::parse_buf(bytes("ffff"), 16u) == some(65535u);
    assert uint::parse_buf(bytes("z"), 36u) == some(35u);

    assert uint::parse_buf(str::bytes("Z"), 10u) == none;
    assert uint::parse_buf(str::bytes("_"), 2u) == none;
}

#[test]
fn test_next_power_of_two() {
    assert (uint::next_power_of_two(0u) == 0u);
    assert (uint::next_power_of_two(1u) == 1u);
    assert (uint::next_power_of_two(2u) == 2u);
    assert (uint::next_power_of_two(3u) == 4u);
    assert (uint::next_power_of_two(4u) == 4u);
    assert (uint::next_power_of_two(5u) == 8u);
    assert (uint::next_power_of_two(6u) == 8u);
    assert (uint::next_power_of_two(7u) == 8u);
    assert (uint::next_power_of_two(8u) == 8u);
    assert (uint::next_power_of_two(9u) == 16u);
    assert (uint::next_power_of_two(10u) == 16u);
    assert (uint::next_power_of_two(11u) == 16u);
    assert (uint::next_power_of_two(12u) == 16u);
    assert (uint::next_power_of_two(13u) == 16u);
    assert (uint::next_power_of_two(14u) == 16u);
    assert (uint::next_power_of_two(15u) == 16u);
    assert (uint::next_power_of_two(16u) == 16u);
    assert (uint::next_power_of_two(17u) == 32u);
    assert (uint::next_power_of_two(18u) == 32u);
    assert (uint::next_power_of_two(19u) == 32u);
    assert (uint::next_power_of_two(20u) == 32u);
    assert (uint::next_power_of_two(21u) == 32u);
    assert (uint::next_power_of_two(22u) == 32u);
    assert (uint::next_power_of_two(23u) == 32u);
    assert (uint::next_power_of_two(24u) == 32u);
    assert (uint::next_power_of_two(25u) == 32u);
    assert (uint::next_power_of_two(26u) == 32u);
    assert (uint::next_power_of_two(27u) == 32u);
    assert (uint::next_power_of_two(28u) == 32u);
    assert (uint::next_power_of_two(29u) == 32u);
    assert (uint::next_power_of_two(30u) == 32u);
    assert (uint::next_power_of_two(31u) == 32u);
    assert (uint::next_power_of_two(32u) == 32u);
    assert (uint::next_power_of_two(33u) == 64u);
    assert (uint::next_power_of_two(34u) == 64u);
    assert (uint::next_power_of_two(35u) == 64u);
    assert (uint::next_power_of_two(36u) == 64u);
    assert (uint::next_power_of_two(37u) == 64u);
    assert (uint::next_power_of_two(38u) == 64u);
    assert (uint::next_power_of_two(39u) == 64u);
}

#[test]
fn test_overflows() {
    assert (uint::max_value > 0u);
    assert (uint::min_value <= 0u);
    assert (uint::min_value + uint::max_value + 1u == 0u);
}

#[test]
fn test_div() {
    assert(uint::div_floor(3u, 4u) == 0u);
    assert(uint::div_ceil(3u, 4u)  == 1u);
    assert(uint::div_round(3u, 4u) == 1u);
}