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RUST QUESTIONS

Why does "move" in Rust not actually move?
Why does "move" in Rust not actually move?
To fix the issue you can do A move is a memcpy followed by treating the source as non-existent.Your big array is on the stack. That's just the way Rust's memory model works: local variables are on the stack. Since the stack space of foo is going away
TAG : rust
Date : November 20 2020, 07:00 PM , By : Shwilly Kidd
What does 0u8 mean in Rust?
What does 0u8 mean in Rust?
Hope that helps Suffixed Literals After searching, I've found this explanation in the same book:
TAG : rust
Date : November 09 2020, 07:01 PM , By : Bhavesh Jamariya
Join iterator of &str
Join iterator of &str
fixed the issue. Will look into that further You could use the itertools crate for that. I use the intersperse helper in the example, it is pretty much the join equivalent for iterators.cloned() is needed to convert str items to str items, it is not
TAG : rust
Date : October 24 2020, 06:10 PM , By : w.rob
Is there any compiler flag to force undefined behavior for signed integer overflow?
Is there any compiler flag to force undefined behavior for signed integer overflow?
hop of those help? Integer overflow in Rust never triggers undefined behaviour, in contrast to C. When compiling in debug mode, arithmetic operations check for overflow and panic, but in release mode there are no checks. The behaviour can be controll
TAG : rust
Date : October 23 2020, 06:10 AM , By : Joanna Marie Pangili
Why doesn't a move closure take ownership of a variable?
Why doesn't a move closure take ownership of a variable?
will help you The Rust Programming Language says: , The answer is given in the error message of your first example
TAG : rust
Date : October 21 2020, 06:10 AM , By : Taylor
undefined reference to `printf' in Rust
undefined reference to `printf' in Rust
This might help you solved it adding rustflags = ["-C", "link-args=-lc"] to .cargo/config under the package root directory.
TAG : rust
Date : October 14 2020, 01:00 AM , By : sine
Check if Rust is running a test build
Check if Rust is running a test build
Hope this helps I can use cfg!(debug_assertions) to check if the Rust project is running in development mode, but I'd like to know how to check if a test is being run. Is there a similar flag for tests I can use in an if statement? , You can use cfg!
TAG : rust
Date : October 13 2020, 09:00 PM , By : willy0229
How can I run a set of functions concurrently on a recurring interval without running the same function at the same time
How can I run a set of functions concurrently on a recurring interval without running the same function at the same time
like below fixes the issue You can achieve this by joining your worker futures such that they all run in parallel, but must all finish together. You can then join that with a delay of 1 second for the same rationale. Wrap that into a loop to run it f
TAG : rust
Date : October 13 2020, 12:00 PM , By : Aparna
Is it theoretically possible to specialise trait behaviour?
Is it theoretically possible to specialise trait behaviour?
hope this fix your issue It is possible on nightly with the still unstable specialization feature and a default implementation (see also the tracking issue for specialization):
TAG : rust
Date : October 13 2020, 09:00 AM , By : haliana H
Why does the compiler prevent me from using push on a Vec created using collect()?
Why does the compiler prevent me from using push on a Vec created using collect()?
will be helpful for those in need If you read the documentation for Vec::push and look at the signature of the method, you will learn that it does not return the Vec:
TAG : rust
Date : October 12 2020, 10:00 PM , By : Ampersand
How do I modify the response body in an actix-web 1.0 middleware?
How do I modify the response body in an actix-web 1.0 middleware?
wish help you to fix your issue You can try one of these two approaches. Both of them work for me: Use map_body method from ServiceResponse:
TAG : rust
Date : October 12 2020, 08:00 AM , By : Devi Vara Prasad Put
How to store a hyper::server::Server as a field in a struct?
How to store a hyper::server::Server as a field in a struct?
will help you The problem is due to a type mismatch. In Rust, a type parameter is part of the type of a struct, so the type parameters for the server in your struct must match the ones you defined in your struct. In your case they don't. There are 2
TAG : rust
Date : October 12 2020, 05:00 AM , By : Akshaya Satapathy
How to format a byte into a 2 digit hex string, in Rust
How to format a byte into a 2 digit hex string, in Rust
seems to work fine As documented in the std::fmt module:
TAG : rust
Date : October 12 2020, 02:00 AM , By : A. Moser
Is "this represents potential undefined behavior in your code" error when using a match arm guard a bug in the
Is "this represents potential undefined behavior in your code" error when using a match arm guard a bug in the
this one helps. This error looks like a limitation of the borrow checker to me, similar to Double mutable borrow error in a loop happens even with NLL on. I can't see how this could lead to a soundness hole, and believe the code is safe.When using an
TAG : rust
Date : October 12 2020, 12:00 AM , By : AlanOmari
How to group_by vector's key
How to group_by vector's key
hop of those help? I want to group a vector by key when the key is a vector. , I'm a novice at Rust and this was a challenge for me
TAG : rust
Date : October 11 2020, 10:00 PM , By : Harold Portocarrero
Why doesn't Rust support overloading function or method?
Why doesn't Rust support overloading function or method?
I think the issue was by ths following , I would argue that in some way Rust does have function and method overloading.Let's say you want to implement an abs() function that can either take an integer or a floating-point number. In C++, you could use
TAG : rust
Date : October 11 2020, 10:00 PM , By : Jiya Malik
How can I add 1 to a generic T?
How can I add 1 to a generic T?
Hope that helps Below is a generic type Foo. How can I correctly implement the addOne method: , You can do it with the help of the num crate:
TAG : rust
Date : October 11 2020, 07:00 PM , By : tahmid chy
How to create a new blockchain project based on CENNZnet?
How to create a new blockchain project based on CENNZnet?
like below fixes the issue I would like to create a new blockchain project based on Substrate and integrate it with modules provided by CENNZnet such as GenericAsset and CENNZX-Spot module. , (Disclosure: I am one of the core developer of CENNZnet)
TAG : rust
Date : October 11 2020, 06:00 PM , By : okaerinasai
Why is it not possible to update a value in a HashMap using bracket [ ] notation?
Why is it not possible to update a value in a HashMap using bracket [ ] notation?
Does that help In Rust the operators can be overloaded by the standard operator traits. The index operator (or sometimes called as subscript operator) has two flavours: Index and IndexMut. If you are looking at the documentation of the HashMap it onl
TAG : rust
Date : October 11 2020, 09:00 AM , By : Daniel H
Where will String::from("") be allocated in a match arm?
Where will String::from("") be allocated in a match arm?
I hope this helps you . Only the matching arm will be evaluated. The non matching arms have no cost apart the size of the program. In the general case, it's not even possible to evaluate other arms, as they depend on data read using destructuring of
TAG : rust
Date : October 11 2020, 02:00 AM , By : Vahid.Sobhani
Rustlings thread exercise, why do I NOT dereference Mutex(Struct)?
Rustlings thread exercise, why do I NOT dereference Mutex(Struct)?
To fix this issue status_shared is of type MutexGuard. MutexGuard implements the DerefMut and Deref traits, with a deref target of T (the type which is stored inside the Mutex - JobStatus in your case.When you use behind a . behind an object the rust
TAG : rust
Date : October 11 2020, 02:00 AM , By : Pinku Raj
Why can't I divide a BigInt with another BigInt and save it to a variable I've initialized with zero?
Why can't I divide a BigInt with another BigInt and save it to a variable I've initialized with zero?
hop of those help? I have the following code snippet: , and instead tells me that I can't divide a BigInt with a BigInt
TAG : rust
Date : October 10 2020, 07:00 PM , By : Indranil Maity
bash: gdb: No such file or directory
bash: gdb: No such file or directory
I think the issue was by ths following , From immediately below that command in the documentation you linked:
TAG : rust
Date : October 10 2020, 07:00 PM , By : Qingyu
What order is `on_initialize` invoked across different modules in a Substrate runtime?
What order is `on_initialize` invoked across different modules in a Substrate runtime?
around this issue The on_initialize function for each Substrate runtime module is called via the Executive module, which handles all of the top-level stuff; essentially just executing blocks/extrinsics.Every time a block is executed (execute_block),
TAG : rust
Date : October 10 2020, 03:00 PM , By : passionli
How can I implement traits for type aliases?
How can I implement traits for type aliases?
this one helps. Creating a type alias does not create an entirely new type, it just allows you to refer to the existing type via a different name. Therefore, trying to implement Debug for MyFn is exactly the same as trying to implement it for Box boo
TAG : rust
Date : October 10 2020, 11:00 AM , By : Nilesh Kandalgaonaka
How can I display a compiler warning upon function invocation?
How can I display a compiler warning upon function invocation?
like below fixes the issue The must_use seems to be fitting here and allows to specify a custom message:
TAG : rust
Date : October 10 2020, 09:00 AM , By : Sathurjan Sathu
Why is it impossible to dereference a boxed iterator trait object?
Why is it impossible to dereference a boxed iterator trait object?
This might help you It is impossible to move any trait object (the dyn Iterator part of your type) out from behind a pointer (dyn Iterator, Box). This is because trait objects are unsized – the compiler does not have information about the concrete si
TAG : rust
Date : October 10 2020, 06:00 AM , By : how to write the reg
How to build a dependency with a different version of the Rust compiler?
How to build a dependency with a different version of the Rust compiler?
To fix the issue you can do You cannot. Rust does not have a stable ABI and it is not possible to mix crates built with different versions of the compiler within the same project. As of 2019, there is no plan to stabilize the ABI.You must compile the
TAG : rust
Date : October 10 2020, 06:00 AM , By : eboy
Why doesn't the borrowed value live long enough when created in constructor in lifetime-annotated impl block?
Why doesn't the borrowed value live long enough when created in constructor in lifetime-annotated impl block?
should help you out I ended up using Vec as kind of linked list, so I don't have to implement my own. If you are reading this, I strongly recommend you to read Learn Rust With Entirely Too Many Linked Lists as @Jmb suggested.This solution kind of avo
TAG : rust
Date : October 09 2020, 10:00 PM , By : bluebee
i need to push (Vec) of a member of struct contained, he is a struct as well
i need to push (Vec) of a member of struct contained, he is a struct as well
wish helps you I am trying to add a member of a structure that is itself a structure. I have the classic mistake "can not move out of borrowed content". , Right, so your:
TAG : rust
Date : October 09 2020, 08:00 PM , By : Ronny Renggo Saputro
How can I invoke a Java method from Rust via JNI?
How can I invoke a Java method from Rust via JNI?
should help you out Here is a simple one-file project to demonstrate how to use the jni crate:Java side
TAG : rust
Date : October 09 2020, 08:00 PM , By : Augustine Shin
Why is the width ignored for my custom formatter implementation?
Why is the width ignored for my custom formatter implementation?
seems to work fine By using write! in your fmt implementation, you are overriding the format provided by its caller.Instead you should call fmt on the strings themselves:
TAG : rust
Date : October 09 2020, 07:00 PM , By : Count of Monte Crist
"use of undeclared type or module" when using Diesel's `belongs_to` attribute
"use of undeclared type or module" when using Diesel's `belongs_to` attribute
hop of those help? As the error mentions, birds is not in scope. The table! macro creates a public module (birds), which you then need to bring into scope to be able to derive Associations (in models.rs):
TAG : rust
Date : October 09 2020, 03:00 PM , By : J.Lee
how to replace member of a structure using this member's method which consume this member itself?
how to replace member of a structure using this member's method which consume this member itself?
wish of those help You can use the take_mut crate to do that elegantly:
TAG : rust
Date : October 09 2020, 10:00 AM , By : Huda Jawed
Which Rust 1.2 containers support trait objects?
Which Rust 1.2 containers support trait objects?
like below fixes the issue Containers that support trait objects are containers that have a ?Sized bound on their containee type.By default with generics, all types are Sized implicitly as this is what you want most of the time, and adding a Sized on
TAG : rust
Date : October 09 2020, 08:00 AM , By : Isiphile Ndzuza
If f32 is not Eq, why does this compile?
If f32 is not Eq, why does this compile?
seems to work fine The eq method (which is called when you use the == operator) is part of the PartialEq trait, not Eq.The Eq trait inherits all of its methods from PartialEq, adding none of its own, and its sole purpose is as a marker to assert that
TAG : rust
Date : October 08 2020, 12:00 PM , By : K Norris
Why does Command.output() execution sometimes return None for status.code()
Why does Command.output() execution sometimes return None for status.code()
seems to work fine Read the manual:
TAG : rust
Date : October 08 2020, 08:00 AM , By : Dylan Hercher
Why my code of lifetime function call is ok or fail?
Why my code of lifetime function call is ok or fail?
I wish this help you Strings "ajoisd" and "aso" have the 'static lifetime. They outlive any variable in the program. Variables x and y in the first block live only in this block which is less than the lifetime of z.
TAG : rust
Date : October 08 2020, 01:00 AM , By : SSOAPI
Consolidating multiple copies of a character at start of string into one in Rust
Consolidating multiple copies of a character at start of string into one in Rust
wish help you to fix your issue I'm working on a parser for a mini language, and I have the need to differentiate between plain strings ("hello") and strings that are meant to be operators/commands, and start with a specific sigil character (e.g. "$a
TAG : rust
Date : October 07 2020, 11:00 PM , By : Akshay Vernekar
Shadowing in Rust and Fighting the Borrow Checker
Shadowing in Rust and Fighting the Borrow Checker
Does that help I'm new to rust. Every time I take user input I created a new variable (via shadowing) to get the input. I think this is inefficient and not the purpose of shadowing, how else can I efficiently reuse the variable input? , The error tel
TAG : rust
Date : October 07 2020, 11:00 PM , By : Fepsy C
How to add or multiply two i16 in Rust to form an i32 without overflowing?
How to add or multiply two i16 in Rust to form an i32 without overflowing?
wish help you to fix your issue There are no integral promotions or implicit casts in Rust, so you must do all type conversions manually.For casts, you can use as . However, if the destination type is a superset of the original one and converting it
TAG : rust
Date : October 07 2020, 07:00 PM , By : vipin kumar
How are Tuples destructured into references?
How are Tuples destructured into references?
I hope this helps . The compiler is helping us using match ergonomics. Match ergonomics applies to tuple destructuring and the match expression; we'll look at the case of the match expression first.Match ergonomics simplifies how Rust binds variables
TAG : rust
Date : October 07 2020, 07:00 PM , By : FCS
Borrowed value does not live long enough (&str -> Option<&str>)
Borrowed value does not live long enough (&str -> Option<&str>)
will help you I think this would make a lot more sense if you kept track of indexes into the passed in string and then returned a slice of that string with:
TAG : rust
Date : October 07 2020, 07:00 PM , By : Michael Ha
Why does a comment without fences trigger a doctest?
Why does a comment without fences trigger a doctest?
Hope this helps This behavior is actually explained in the documentation. In the very bottom it says (emphasis mine):
TAG : rust
Date : October 07 2020, 03:00 PM , By : Zlatko Pazdrijan
How to build the docs.rs documentation of an FFI crate when the native library is not present?
How to build the docs.rs documentation of an FFI crate when the native library is not present?
To fix the issue you can do The about page of docs.rs gives more information about that. You can actually enable a specific feature (among other things) during the docs.rs doc generation. An example explains well how to achieve that:Cargo.toml:
TAG : rust
Date : October 07 2020, 03:00 PM , By : user6044675
How does the borrow checker deal with a reference returned from a function?
How does the borrow checker deal with a reference returned from a function?
like below fixes the issue I'm new to Rust and I'm reading the The Rust Programming Language online book. I'm now stuck on a problem about the Rust's borrow check, the code example is shown below: , When you have
TAG : rust
Date : October 07 2020, 08:00 AM , By : María sanchez
Why doesn't Dbg seem to work within a for_each loop?
Why doesn't Dbg seem to work within a for_each loop?
I hope this helps you . dbg! returns the value you passed in, while for_each requires a unit type to be returned. println! returns a unit type.We can make this work by adding ;:
TAG : rust
Date : October 07 2020, 07:00 AM , By : G Sharma
When I run my rust application on windows the coloring works with cargo run but it compeltely breaks when directly using
When I run my rust application on windows the coloring works with cargo run but it compeltely breaks when directly using
To fix this issue Windows support for VT100 escape sequences (your color codes) was only added with some rather recent update of Windows 10 and must be enabled explicitly for each app, via native API. This is done via the SetConsoleMode function with
TAG : rust
Date : October 07 2020, 05:00 AM , By : mayank
Rust import trait for unqualified usage
Rust import trait for unqualified usage
Does that help You can't.As the compiler very explicitly tells you, methods cannot be imported directly:
TAG : rust
Date : October 07 2020, 05:00 AM , By : Kartik Raj
How to get the roothash or a proof from a child trie in substrate?
How to get the roothash or a proof from a child trie in substrate?
should help you out The srml_support::storage::child API make use of sr_io API.sr_io provides more functionality, for example sr_io::child_storage_root which is the function you are looking for.
TAG : rust
Date : October 07 2020, 05:00 AM , By : Christof Vanden Eynd
Is there a way to give a parameter back to the caller if the method fails, instead of panicking?
Is there a way to give a parameter back to the caller if the method fails, instead of panicking?
may help you . A common idiom is to return the item as the Err variant of a Result, or embedded in it (like is used in std::sync::Arc::try_unwrap, so you could do something like:
TAG : rust
Date : October 06 2020, 08:00 PM , By : Ting-Hao Chen
Holding simultaneous references to different elements of a container
Holding simultaneous references to different elements of a container
will be helpful for those in need So the goal is to overwrite vec[0] with vec[0] + vec[1] ?I think the trick is to use indexes into the Vec, instead of holding the references open.
TAG : rust
Date : October 06 2020, 01:00 PM , By : IuKing Saw
To convert a ethereum_types::H256 to String in Rust
To convert a ethereum_types::H256 to String in Rust
around this issue This (weird) behaviour comes from the fixed-hash crate.It implements several formatting traits:
TAG : rust
Date : October 06 2020, 10:00 AM , By : Renee Buckles
Could not work out a closure returned from a method capturing a member variable
Could not work out a closure returned from a method capturing a member variable
wish of those help The first, why does the function closure restricting my closure?
TAG : rust
Date : October 06 2020, 10:00 AM , By : Santosh
What is the difference between Rc<RefCell<T>> and RefCell<Rc<T>>?
What is the difference between Rc<RefCell<T>> and RefCell<Rc<T>>?
hop of those help? The Rust documentation covers Rc pretty extensively but doesn't go into RefCell, which I am now encountering. , Do these effectively give the same result?
TAG : rust
Date : October 06 2020, 07:00 AM , By : Vuur
Is using to_string the cleanest way to read a file by lines and split by whitespace?
Is using to_string the cleanest way to read a file by lines and split by whitespace?
I hope this helps you . Your code is generally idiomatic and good, I just have a few minor caveats. As far as the "overwork", I would argue modifying the string in-place is overwork, since at every removed whitespace character, you either need to do
TAG : rust
Date : October 06 2020, 04:00 AM , By : Chandu Vemula
Why am I able to call a closure twice even though I have moved a variable into it?
Why am I able to call a closure twice even though I have moved a variable into it?
Hope that helps , The variable a has indeed been moved into the closure:
TAG : rust
Date : October 05 2020, 03:00 PM , By : Daker
How do I used the colored crate with non-static strings?
How do I used the colored crate with non-static strings?
will help you You can not use the color methods on the format string, which is required to be a string literal by the compiler. You have to use it on the arguments. Like this:
TAG : rust
Date : October 05 2020, 10:00 AM , By : guy
Using a previously borrowed Result in Rust
Using a previously borrowed Result in Rust
wish help you to fix your issue I'd like to enhance an error message with the contents of a previous Ok, if that was the previous Result, but I found no obvious way of going about it. To demonstrate the issue, I've written the following functions eul
TAG : rust
Date : October 05 2020, 08:00 AM , By : amy commands
How to create an iterator over Vec<Vec<T>> of unknown size that is equivalent of cartesian product of iterat
How to create an iterator over Vec<Vec<T>> of unknown size that is equivalent of cartesian product of iterat
wish help you to fix your issue The doc already answer you:
TAG : rust
Date : October 05 2020, 07:00 AM , By : Tommy1203

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