New benchmark tests in vec.rs:
`push`, `starts_with_same_vector`, `starts_with_single_element`,
`starts_with_diff_one_element_end`, `ends_with_same_vector`,
`ends_with_single_element`, `ends_with_diff_one_element_beginning` and
`contains_last_element`
This adds `get_opt` to `std::vec`, which looks up an item by index and returns an `Option`. If the given index is out of range, `None` will be returned, otherwise a `Some`-wrapped item will be returned.
Example use case:
```rust
use std::os;
fn say_hello(name: &str) {
println(fmt!("Hello, %s", name));
}
fn main(){
// Try to get the first cmd line arg, but default to "World"
let args = os::args();
let default = ~"World";
say_hello(*args.get_opt(1).unwrap_or(&default));
}
```
If there's an existing way of implementing this pattern that's cleaner, I'll happily close this. I'm also open to naming suggestions (`index_opt`?)
std::vec: Sane implementations for connect_vec and concat_vec
Avoid unnecessary copying of subvectors, and calculate the needed space
beforehand. These implementations are simple but better than the
previous.
Also only implement it once, for all `Vector<T>` using:
impl<'self, T: Clone, V: Vector<T>> VectorVector<T> for &'self [V]
Closes#9581
Avoid unnecessary copying of subvectors, and calculate the needed space
beforehand. These implementations are simple but better than the
previous.
Also only implement it once, for all `Vector<T>` using:
impl<'self, T: Clone, V: Vector<T>> VectorVector<T> for &'self [V]
performance improved according to the bench test:
before
test vec::bench::concat ... bench: 74818 ns/iter (+/- 408)
test vec::bench::connect ... bench: 87066 ns/iter (+/- 376)
after
test vec::bench::concat ... bench: 17724 ns/iter (+/- 126)
test vec::bench::connect ... bench: 18353 ns/iter (+/- 691)
Closes#9581
std::vec: Use a valid value as lifetime dummy in iterator
The current implementation uses `&v[0]` for the lifetime struct field,
but that is a dangling pointer for iterators derived from zero-length
slices.
Example:
let v: [int, ..0] = []; println!("{:?}", v.iter())
std::vec::VecIterator<,int>{ptr: (0x7f3768626100 as *()), end: (0x7f3768626100 as *()), lifetime: &139875951207128}
To replace this parameter, use a field of type `Option<&'self ()>`
that is simply initialized with `None`, but still allows the iterator to
have a lifetime parameter.
The current implementation uses `&v[0]` for the lifetime struct field,
but that is a dangling pointer for iterators derived from zero-length
slices.
Example:
let v: [int, ..0] = []; println!("{:?}", v.iter())
std::vec::VecIterator<,int>{ptr: (0x7f3768626100 as *()), end: (0x7f3768626100 as *()), lifetime: &139875951207128}
To replace this parameter, use a field of type `Option<&'self ()>`
that is simply initialized with `None`, but still allows the iterator to
have a lifetime parameter.
`push_bytes` is implemented with `ptr::copy_memory` here since this
function is intended to be used to implement `.push_str()` for str, so
we want to avoid the overhead.
Issue #8742
Add the method `.reserve_additional(n: uint)`: Check for overflow in
self.len() + n, and reserve that many elements (rounded up to next power
of two). Does nothing if self.len() + n < self.capacity() already.
Visit the free functions of std::vec and reimplement or remove some. Most prominently, remove `each_permutation` and replace with two iterators, ElementSwaps and Permutations.
Replace unzip, unzip_slice with an updated `unzip` that works with an iterator argument.
Replace each_permutation with a Permutation iterator. The new permutation iterator is more efficient since it uses an algorithm that produces permutations in an order where each is only one element swap apart, including swapping back to the original state with one swap at the end.
Unify the seldomly used functions `build`, `build_sized`, `build_sized_opt` into just one function `build`.
Remove `equal_sizes`
These functions have very few users since they are mostly replaced by
iterator-based constructions.
Convert a few remaining users in-tree, and reduce the number of
functions by basically renaming build_sized_opt to build, and removing
the other two. This for both the vec and the at_vec versions.
The basic construct x.len() == y.len() is just as simple.
This function used to be a precondition (not sure about the
terminology), so it had to be a function. This is not relevant any more.
Update for a lot of changes (not many free functions left), add examples
of the important methods `slice` and `push`, and write a short bit about
iteration.
Introduce ElementSwaps and Permutations. ElementSwaps is an iterator
that for a given sequence length yields the element swaps needed
to visit each possible permutation of the sequence in turn.
We use an algorithm that generates a sequence such that each permutation
is only one swap apart.
let mut v = [1, 2, 3];
for perm in v.permutations_iter() {
// yields 1 2 3 | 1 3 2 | 3 1 2 | 3 2 1 | 2 3 1 | 2 1 3
}
The `.permutations_iter()` yields clones of the input vector for each
permutation.
If a copyless traversal is needed, it can be constructed with
`ElementSwaps`:
for (a, b) in ElementSwaps::new(3) {
// yields (2, 1), (1, 0), (2, 1) ...
v.swap(a, b);
// ..
}
