The foldl based implementation allocates lots of unneeded vectors.
iter::map_to_vec is already optimized to avoid these.
One place that benefits quite a lot from this is the metadata decoder, helping with compile times for tiny programs.
The current protocol is very comparable to Python, where `.__iter__()` returns an iterator object which implements `.__next__()` and throws `StopIteration` on completion. `Option` is much cleaner than using a exceptions as a flow control hack though. It requires that the container is frozen so there's no worry about invalidating them.
Advantages over internal iterators, which are functions that are passed closures and directly implement the iteration protocol:
* Iteration is stateful, so you can interleave iteration over arbitrary containers. That's needed to implement algorithms like zip, merge, set union, set intersection, set difference and symmetric difference. I already used this internally in the `TreeMap` and `TreeSet` implementations, but regions and traits weren't solid enough to make it generic yet.
* They provide a universal, generic interface. The same trait is used for a forward/reverse iterator, an iterator over a range, etc. Internal iterators end up resulting in a trait for each possible way you could iterate.
* They can be composed with adaptors like `ZipIterator`, which also implement the same trait themselves.
The disadvantage is that they're a pain to write without support from the compiler for compiling something like `yield` to a state machine. :)
This can coexist alongside internal iterators since both can use the current `for` protocol. It's easier to write an internal iterator, but external ones are far more powerful/useful so they should probably be provided whenever possible by the standard library.
## Current issues
#5801 is somewhat annoying since explicit type hints are required.
I just wanted to get the essentials working well, so I haven't put much thought into making the naming concise (free functions vs. static `new` methods, etc.).
Making an `Iterable` trait seems like it will have to be a long-term goal, requiring type system extensions. At least without resorting to objects which would probably be unacceptably slow.
This restores the trait that was lost in 216e85fadf. `Num` will eventually be broken up into a more fine-grained trait hierarchy in the future once a design can be agreed upon.
To contribute to the discussion about the future of Rust's numeric traits, please see issue #4819 and the [wiki page](https://github.com/mozilla/rust/wiki/Bikeshed-Numeric-Traits).
I have also switched to [implementing NumCast using macros](353ce872e2). This removes a significant number of lines of code.
This restores the trait that was lost in 216e85fadf. It will eventually be broken up into a more fine-grained trait hierarchy in the future once a design can be agreed upon.
As proposed in issue #5632.
I added some new stuff to libc - hopefully correctly. I only added a single signal constant (SIGKILL) because adding more seems complicated by differences between platforms - and since it is not required for issue #5632 then I figure that I can use a further pull request to flesh out the SIG* constants more.
r? @graydon This is preliminary work on bringing rustpkg up to conformance with #5679
and related issues.
This change makes rustpkg infer a package ID from its containing directory,
instead of requiring name and vers attributes in the code. Many aspects of it
are incomplete; I've only tested one package (see README.txt) and one command,
"build". So far it only works for local packages.
I also removed code for several of the package commands other than "build",
replacing them with stubs that fail, since they used package IDs in ways that
didn't jibe well with the new scheme. I will re-implement the commands one
at a time.
This refactors much of the ast generation required for `deriving` instances into a common interface, so that new instances only need to specify what they do with the actual data, rather than worry about naming function arguments and extracting fields from structs and enum. (This all happens in `generic.rs`. I've tried to make sure it was well commented and explained, since it's a little abstract at points, but I'm sure it's still a little confusing.)
It makes instances like the comparison traits and `Clone` short and easy to write.
Caveats:
- Not surprisingly, this slows the expansion pass (in some cases, dramatically, specifically deriving Ord or TotalOrd on enums with many variants). However, this shouldn't be too concerning, since in a more realistic case (compiling `core.rc`) the time increased by 0.01s, which isn't worth mentioning. And, it possibly slows type checking very slightly (about 2% worst case), but I'm having trouble measuring it (and I don't understand why this would happen). I think this could be resolved by using traits and encoding it all in the type system so that monomorphisation handles everything, but that would probably be a little tricky to arrange nicely, reduce flexibility and make compiling rustc take longer. (Maybe some judicious use of `#[inline(always)]` would help too; I'll have a bit of a play with it.)
- The abstraction is not currently powerful enough for:
- `IterBytes`: doesn't support arguments of type other than `&Self`.
- `Encodable`/`Decodable` (#5090): doesn't support traits with parameters.
- `Rand` & `FromStr`; doesn't support static functions and arguments of type other than `&Self`.
- `ToStr`: I don't think it supports returning `~str` yet, but I haven't actually tried.
(The last 3 are traits that might be nice to have: the derived `ToStr`/`FromStr` could just read/write the same format as `fmt!("%?", x)`, like `Show` and `Read` in Haskell.)
I have ideas to resolve all of these, but I feel like it would essentially be a simpler version of the `mt` & `ty_` parts of `ast.rs`, and I'm not sure if the simplification is worth having 2 copies of similar code.
Also, makes Ord, TotalOrd and TotalEq derivable (closes#4269, #5588 and #5589), although a snapshot is required before they can be used in the rust repo.
If there is anything that is unclear (or incorrect) either here or in the code, I'd like to get it pointed out now, so I can explain/fix it while I'm still intimately familiar with the code.
This implements #5158. Currently it takes the command line args and the crate map. Since it doesn't take a `main` function pointer, you can't actually start the runtime easily, but that seems to be a shim to allow the current `rust_start` function to call into main.
However, you can do an end-run round the io library and do this:
```rust
use core::libc::{write, c_int, c_void, size_t, STDOUT_FILENO};
#[start]
fn my_start(_argc:int, _argv: **u8, _crate_map: *u8) -> int {
do str::as_buf("Hello World!\n") |s,len| {
unsafe {
write(STDOUT_FILENO, s as *c_void, len as size_t);
}
}
return 0;
}
```
Which is the most basic "Hello World" you can do in rust without starting up the runtime (though that has quite a lot to do with the fact that `core::io` uses `@` everywhere...)
Allow a deriving instance using the generic code to short-circuit for
any non-matching enum variants (grouping them all into a _ match),
reducing the number of arms required. Use this to speed up the Eq &
TotalEq implementations.
Pulls out many of the common patterns from the Eq and Clone deriving code (and
invents a few of its own), so that deriving instances are very easy to write
for a certain class of traits. (Basically, those which don't have parameters
and where all methods only take arguments of type `&Self` and return either
`Self` or types with no parameters.)
The code samples are xfail'ed because the buildbot won't have `libsnappy.so` and I don't want to add boilerplate to all the snippets (but they're directly from my snappy bindings so I'll just send a pull request whenever they break). It works really well as an example because it's tiny library and lets the caller manage all the buffers.
I think everything stated in the `Interoperability with foreign code` section is accurate but it deserves a thorough double-check :).
The example with OpenSSL is incorrect, because OpenSSL is using a
static variable for the return value and isn't thread-safe.
The gettimeofday example isn't great because it's not very portable.
This is preliminary work on bringing rustpkg up to conformance with #5679
and related issues.
This change makes rustpkg infer a package ID from its containing directory,
instead of requiring name and vers attributes in the code. Many aspects of it
are incomplete; I've only tested one package (see README.txt) and one command,
"build". So far it only works for local packages.
I also removed code for several of the package commands other than "build",
replacing them with stubs that fail, since they used package IDs in ways that
didn't jibe well with the new scheme. I will re-implement the commands one
at a time.
