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/**
* A deque, for fun. Untested as of yet. Likely buggy.
*/
import std.util;
import std._vec;
import std._int;
type t[T] = obj {
fn size() -> uint;
fn add_front(&T t);
fn add_back(&T t);
fn pop_front() -> T;
fn pop_back() -> T;
fn peek_front() -> T;
fn peek_back() -> T;
fn get(int i) -> T;
};
fn create[T]() -> t[T] {
type cell[T] = mutable util.option[T];
let uint initial_capacity = 32u; // 2^5
/**
* Grow is only called on full elts, so nelts is also len(elts), unlike
* elsewhere.
*/
fn grow[T](uint nelts, uint lo, vec[cell[T]] elts) -> vec[cell[T]] {
check (nelts == _vec.len[cell[T]](elts));
fn fill[T](uint i, uint nelts, uint lo, &vec[cell[T]] old) -> cell[T] {
if (i < nelts) {
ret old.(((lo + i) % nelts) as int);
} else {
ret util.none[T]();
}
}
let uint nalloc = _int.next_power_of_two(nelts + 1u);
let _vec.init_op[cell[T]] copy_op = bind fill[T](_, nelts, lo, elts);
ret _vec.init_fn[cell[T]](copy_op, nalloc);
}
/**
* FIXME (issue #94): We're converting to int every time we index into the
* vec, but we really want to index with the lo and hi uints that we have
* around.
*/
fn get[T](&vec[cell[T]] elts, uint i) -> T {
alt (elts.(i as int)) {
case (util.some[T](t)) { ret t; }
case (_) { fail; }
}
}
obj deque[T](mutable uint nelts,
mutable uint lo,
mutable uint hi,
mutable vec[cell[T]] elts)
{
fn size() -> uint { ret nelts; }
fn add_front(&T t) {
let uint oldlo = lo;
if (lo == 0u) {
lo = _vec.len[cell[T]](elts) - 1u;
} else {
lo -= 1u;
}
if (lo == hi) {
elts = grow[T](nelts, oldlo, elts);
lo = _vec.len[cell[T]](elts) - 1u;
hi = nelts;
}
elts.(lo as int) = util.some[T](t);
nelts += 1u;
}
fn add_back(&T t) {
if (lo == hi && nelts != 0u) {
elts = grow[T](nelts, lo, elts);
lo = 0u;
hi = nelts;
}
elts.(hi as int) = util.some[T](t);
hi = (hi + 1u) % _vec.len[cell[T]](elts);
nelts += 1u;
}
/**
* We actually release (turn to none()) the T we're popping so that we
* don't keep anyone's refcount up unexpectedly.
*/
fn pop_front() -> T {
let T t = get[T](elts, lo);
elts.(lo as int) = util.none[T]();
lo = (lo + 1u) % _vec.len[cell[T]](elts);
ret t;
}
fn pop_back() -> T {
if (hi == 0u) {
hi = _vec.len[cell[T]](elts) - 1u;
} else {
hi -= 1u;
}
let T t = get[T](elts, hi);
elts.(hi as int) = util.none[T]();
ret t;
}
fn peek_front() -> T {
ret get[T](elts, lo);
}
fn peek_back() -> T {
ret get[T](elts, hi - 1u);
}
fn get(int i) -> T {
let uint idx = (lo + (i as uint)) % _vec.len[cell[T]](elts);
ret get[T](elts, idx);
}
}
let vec[cell[T]] v = _vec.init_elt[cell[T]](util.none[T](),
initial_capacity);
ret deque[T](0u, 0u, 0u, v);
}
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