This no longer compiles:
extern crate "my-crate" as my_crate1;
What's the new syntax? I did not find anything by searching.
Can Rust handle cyclic data structures without any garbage collector?
As for the title question - Yes, cyclic data structures can be handled without garbage collector. http://smallcultfollowing.com/babysteps/blog/2015/04/06/modeling-graphs-in-rust-using-vector-indices/ http://featherweightmusings.blogspot.com/2015/04/graphs-in-rust.html For first question. Yes, you can completely avoid garbage collector and manual deallocation in most cases. In some you rely on RC which is a simple form of garbage collection, or unsafe,...
Writing Vec to a file
To do it directly you'd want to use std::slice::from_raw_parts() function: use std::slice; use std::mem; fn main() { let slice_u16: &[u16] = &*vec![1, 2, 3, 4, 5, 6]; println!("u16s: {:?}", slice_u16); let slice_u8: &[u8] = unsafe { slice::from_raw_parts( slice_u16.as_ptr() as *const u8, slice_u16.len() * mem::size_of::<u16>() ) }; println!("u8s: {:?}", slice_u8); }...
Why do I need to use self::core::ops?
An extern crate x; loads x into the current namespace. use statements are absolute paths unless they start with self::, so if you put your extern crate core; anywhere but the crate root then you need to specify an absolute path or use self::. mod foo { mod bar {...
More convenient way to work with strings in winapi calls
In your situation, you always want a maximum of 255 bytes, so you can use an array instead of a vector. This reduces the entire boilerplate to a mem::uninitialized() call, an as_mut_ptr() call and a slicing operation. unsafe { let mut v: [u16; 255] = mem::uninitialized(); let read_len = user32::GetWindowTextW(...
Lifetime of a mutable element in struct
I know this has been answered before, but I can't find it... feel free to mark this as duplicate if you find it. The problem is that you are attempting to store a reference in a container that will outlive the reference. Here's a MCVE of your problem: fn main()...
Recovering from `panic!` in another thread
Putting aside "you should be using Result where possible," yes, this is basically how you catch a panic in Rust. Keep in mind that "recover" is perhaps not the best way of phrasing this in Rust. You don't really recover from panics in Rust, you isolate them, then detect them....
Create a vector from iterating hashmap
Your resulting Vec needs to own the Strings, so remove the & before the user.reference.clone(). Playground URL: https://play.rust-lang.org/?gist=6a6b50ebf589fcce1dbf&version=nightly Gist URL: https://gist.github.com/6a6b50ebf589fcce1dbf...
Create shared C object linked to Rust dylib for use in R
In the C++ code, you need to declare the Rust function (which is available via the C ABI) as extern "C". treble.h #include <stdint.h> extern "C" { int32_t treble(int32_t value); } The error you are getting is because the C++ compiler is name mangling the method treble before attempting to...
the type of this value must be known in this context
On an iterator, the collect method can produce many types of collections: Vec, String and many more. You cannot call the method len() on a value of an unknown type. Specify the type with something like .collect::<Vec<_>>(). Or, when you’re purely wanting to find out how many items there are...
Struct that owns some data and a reference to the data [duplicate]
rust,object-lifetime,borrow-checker
A raw design of the structs based on your requirements might look like this: struct AnotherObj<'a> { original: &'a Vec<i8>, // Let's agree on Vec<i8> as your "data" type. } struct Obj<'a> { original: Vec<i8>, // <-------------------+ processed: AnotherObj<'a>, // should point here --+ } However it's very tricky to...
Casting to a generic type
You simply have to specify T::Output as the return type of the function: fn divide<T: std::ops::Div>(a: T, b: T) -> T::Output { a / b } Edit to add more explanation on why you cannot do the cast inside the function When you are IN your generic function divide, the...
Bug in FFI when passing CString followed by an int
It seems that the 2nd arg is being interpreted (either in rust or c) as sizeof string, rather than the value passed from the Rust code. Correct. You are experiencing undefined behavior here. Your C-Function has a different signature from the extern function you declared in Rust-Code. First of...
Immutable reference after mutable borrow
Your program panics because you're trying to borrow the Vec mutably and immutably at the same time: this is not allowed. What you need to do instead is wrap only the Strings in RefCell. This allows you to mutate the strings while iterating the Vec. use std::cell::RefCell; struct Res {...
What is the idiomatic way to write a linked list with a tail pointer?
linked-list,rust,reference-counting
Yes, if you want to write a singly-linked-list with a tail-pointer you have three choices: Safe and Mutable: Use NodePtr = Option<Rc<RefCell<Node<T>>>> Safe and Immutable: Use NodePtr = Option<Rc<Node<T>>> Unsafe and Mutable: Use tail: *mut Node<T> The *mut is going to be more efficient, and it's not like the Rc...
remove duplicates from vector of custom struct
If you look at the documentation for Vec::dedup, you'll note that it's in a little section marked by the following: impl<T: PartialEq> Vec<T> This means that the methods below it exist only when the given constraints are satisfied. In this case, dedup isn't there because User doesn't implement the PartialEq...
Cargo dependency version syntax
See the crates.io documentation page on "Cargo and crates.io". To summarise: Nothing or a caret (^) means "at least this version, until the next incompatible version". A tilde (~) means "at least this version, until (but excluding) the next minor/major release". That is, ~1.2.3 will accept 1.2.X where X is...
Return a moving window of elements resulting from an iterator of Vec
You can use Vec::retain instead of filter for this, which allows you to keep your Vec: fn main() { let mut buf = vec![ 8, 9, 10, 11, 12, 13, 14, 8, 9, 10, 11, 12, 13, 14, 8, 9, 10, 11, 12, 13, 14, ]; println!("{:?}", buf); buf.retain(|&x| x...
Reading immutable value inside spawned thread
You're almost there. It's just that Arc has to be cloned outside of the spawned thread: for chunk in chunks { let thread_tx = tx.clone(); let user_index_cloned = user_index.clone(); thread::spawn(move || { let result = chunk.iter().map( |row| User { reference: row[user_index_cloned.reference].to_string(), email: row[user_index_cloned.email].to_string() } ).collect::<Vec<User>>(); thread_tx.send(result).unwrap(); }); } This has...
Why is `Sized` bound necessary in this trait?
As you probably already know, types in Rust can be sized and unsized. Unsized types, as their name suggest, do not have a size required to store values of this type which is known to the compiler. For example, [u32] is an unsized array of u32s; because the number of...
Pass Python list to Rust function
Looks like I solved the problem. I turned the Python list into a C array, and passed that to the Rust function. Here is the working code: #[repr(C)] pub struct List_4 { // Create a struct using #[repr(C)], will do the same in Python so it is shareable array: [i32;...
How can I open a file with the standard text editor?
You can use the open crate. It supports Windows, OS X and Linux. To open a text-file on your C: drive, you can use extern crate open; fn main() { open::that("C:\textfile.txt"); } ...
How to reverse after zip two chains
You're looking for the following impl (spoiler: it doesn't exist): impl<A, B> ExactSizeIterator for Chain<A, B> where A: ExactSizeIterator, B: ExactSizeIterator { ... } An ExactSizeIterator must implement only one method, len(&self). So the idea behind an hypothetical implementation would be to sum both lengths so that chain_a_b.len() == a.len()...
Stack behavior when returning a pointer to local variable
You shouldn't be returning a pointer to a local stack variable at all. Doing so is undefined behaviour, and the compiler is completely free to do whatever it wants. When you say unsafe, you are promising the compiler that you will manually uphold all of its expected invariants... and then...
Situations where Cell or RefCell is the best choice
It is not entirely correct to ask when Cell or RefCell should be used over Box and Rc because these types solve different problems. Indeed, more often than not RefCell is used together with Rc in order to provide mutability with shared ownership. So yes, use cases for Cell and...
How can I create Haskell-like functional dependencies
While Haskell has two things to express such relationship between types, fundeps and associated types, Rust has only the latter. Traits in Rust can contain type members which are assigned with concrete values at the implementation site, and the compiler considers them uniquely identified by the combination of type parameters...
How to implement variable increment via side effect?
At present, += is only defined on the primitive integer types; generically, you will need to expand it to *x = *x + 1; instead. This then reveals more problems: <anon>:4:15: 4:16 error: mismatched types: expected `T`, found `_` (expected type parameter, found integral variable) [E0308] <anon>:4 *x = *x...
Implementing a generic conversion from an object implementing the `Error` trait
You don't. That implementation would be a bit useless, anyway. It would mean that all other error types would just be immediately boxed. At that point, you might as well just make use of the existing conversions involving Box<Error> and use that instead. If you want an error type that...
Cannot infer appropriate lifetime for autoderef in Iterator impl
You need to update your get method to return a reference with longer life: // Use 'a from impl<'a> IntegerArrayBag<'a> fn get(&self, idx: usize) -> Option<&'a i32> { and then it will compile....
Value does not live long enough when using multiple threads
The error does look misleading, however, it is correct. Your problem in fact is that chunks() gives an iterator of slices into the original vector, and because you're trying to use this slice in a spawn()ed thread, it must have 'static lifetime, but naturally it does not. You said that...
Rust: Lifetime of String from file [duplicate]
The string bound to "s" will be deallocated once the function ends ("s" goes out of scope), so you cannot return a reference to its contents outside the function. The best way is to return the string itself: fn read_shader_code(string_path: &str) -> String { let path = Path::new(string_path); let display...
Filter vector in place
If you want to remove elements you can use retain(), which removes elements from the vector if the filter function return false: let mut vec = vec![1, 2, 3, 4]; vec.retain(|&x| x%2 == 0); assert_eq!(vec, [2, 4]); If you want to modify the elements in place there is map_in_place() but...
Why does Drop take &mut self instead of self?
Let's look at how std::mem::drop is implemented: pub fn drop<T>(_x: T) { } That's right: it's an empty function! That's because it takes advantage of move semantics to acquire ownership of its argument. If T implements Drop, the compiler automatically inserts a call to Drop::drop(_x) at the end of the...
What is the most appropriate way to convert nibbles to a u64?
Your issue is a simple one: for i in values, where values is of type &Vec<u8>, iterates over references to each value; that is, i is of type &u8. Oring and adding and such with references doesn’t make sense; you need to dereference it, getting the underlying u8. The easiest...
Result has no method called “unwrap()”?
If you read the documentation for Result::unwrap, you'll note that it's under a little section called: impl<T, E: Debug> Result<T, E> This means the methods in that section only exist so long as the given constraints are satisfied. So far as I can see, the only reason unwrap wouldn't exist...
vector method push_all is not found for a custom struct
Look at the definition of push_all: impl<T> Vec<T> where T: Clone { fn push_all(&mut self, other: &[T]); } Appends all elements in a slice to the Vec. Iterates over the slice other, clones each element, and then appends it to this Vec. The other vector is traversed in-order. (Emphasis mine.)...
Why do I have to expose a macro implementation's 'use' in the client library?
Because macro_rules! is a bit dumber than you might expect. It does not, for example, bring imports with it when it expands something. It's best to think of macro expansion as mostly just a dumb copy+paste job. If you look at any reasonably well-written macro that depends on outside symbols,...
Calling an impl method from another impl method
You need to fully qualify the method you are calling. struct St1 { aa: String } impl St1 { pub fn method1() -> String { St1::method2() } pub fn method2() -> String { unimplemented!() } } On the off chance that you mean for these methods to be instance methods,...
How to use multiple variables in routes with Nickel?
You need a separator. For example: #[macro_use] extern crate nickel; use nickel::Nickel; fn main() { let mut server = Nickel::new(); server.utilize(router! { get "/start/:userid/:passwd" => |request, _response| { println!("this is user: {:?} = {:?}", request.param("userid"), request.param("passwd") ); "Hello world!" } }); server.listen("127.0.0.1:6767"); } It looks from your question like you...
Load a shared library linked to Rust library in R
The problem is going to boil down to the fact that your shared libraries are not in the directories that your system expects them to be by default. There are a few tricks that you can use, 2 of which I was able to make work: Run R from the...
“conflicting implementations for trait” when trying to be generic
The problem with your code is that you have a coherence violation in it, and, very likely, any attempts to fix it would lead to new coherence violations. Coherence rules in Rust are somewhat complex, however, they are based on one principle: you can implement "your" traits for arbitrary types...
Can I create a macro that unrolls loops?
Well, sort of. macro_rules! unroll { (0, |$i:ident| $s:stmt) => {}; (1, |$i:ident| $s:stmt) => {{ let $i: usize = 0; $s; }}; (2, |$i:ident| $s:stmt) => {{ unroll!(1, |$i| $s); let $i: usize = 1; $s; }}; (3, |$i:ident| $s:stmt) => {{ unroll!(2, |$i| $s); let $i: usize =...
Conditionally compile only one module at a time
You can run tests specifically for one module by providing it as an argument to the test binary. Cargo passes arguments to the test binary if you specify it after --, so something like this should work: cargo test -- module::you::want::to::test However, you can't compile only a part of a...
Global feature gates in Cargo
No, though you don't add feature gates to every source file; they are crate attributes. That is, you set them on the crate, not on every module.
Modify Collection While Iterating Over it
Is there a way that I could make this code update the board "in place"? There exists a type specially made for situations such as these. It's coincidentally called std::cell::Cell. You're allowed to mutate the contents of a Cell even when it has been immutably borrowed multiple times. Cell...
Implement Debug trait for large array type
use std::fmt; struct Array<T> { data: [T; 1024] } impl<T: fmt::Debug> fmt::Debug for Array<T> { fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result { self.data[..].fmt(formatter) } } fn main() { let array = Array { data: [0u8; 1024] }; println!("{:?}", array); } It's not possible to implement Debug for [T; 1024]...
Renaming a crate with a hyphen doesn't compile anymore
Dashes in extern crate names can be replaced with underscores. So your example should be extern crate my_crate as my_crate1; Or if you want the underscored name, using the following will work extern crate my_crate; ...
cannot move out of borrowed content - ref doesn't work [duplicate]
Short answer The function fn2 receives a reference to a MyEnum1 as a parameter, but the Struct1 contains an owned MyEnum1. This means that you are actually trying to turn a reference into an owned value, which is only possible if you copy the data. Long answer Your code would...
How can I send a function to another thread?
multithreading,unit-testing,rust
There are several problems with your code, I'll show you how to fix them one by one. The first problem is that you're using map() to iterate over an iterator. It won't work correctly because map() is lazy - unless you consume the iterator, the closure you passed to it...
Struct vs enum lifetime differences
To me it seems like let c = Bar::Fub(&17), the 17 lasts the same life time as the previous line where "Foo" is created on the stack A string literal always has 'static lifetime and will therefor always live long enough. I think the issue is that you are...
Indexing a String
Indeed, the size of a [u8] isn't known at compile time. The size of &[u8] however is known at compile time because it's just a pointer plus a usize representing the length of sequence. format!("{:?}/{:?}", &bytes[0..2], &bytes[2..4]) Rust strings are encoded in utf-8, so working with strings in this way...