fn | Scala-like functional programming helpers for C11 | Functional Programming library
kandi X-RAY | fn Summary
kandi X-RAY | fn Summary
fn is a collection of functional programming helpers for C++11, inspired by Scala. It's header only and has no dependecies. It is efficient, lightweight and convenient (compared to the STL's ). fn provides a lazy evaluated view (similar to Scala's view) on which you can apply the usual functional programming tasks, including but not limited to filter, map, reduce, zip, fold_left, flat_map and for_all. Views are iteratble.
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Trending Discussions on fn
QUESTION
I was following along with this tutorial on creating a concurrent counter struct for a usize
value: ConcurrentCounter
. As I understand it, this wrapper struct allows us to mutate our usize
value, with more concise syntax, for example:my_counter.increment(1)
vs. my_counter.lock().unwrap().increment(1)
.
Now in this tutorial our value is of type usize
, but what if we wanted to use a f32
, i32
, or u32
value instead?
I thought that I could do this with generic type arguments:
...ANSWER
Answered 2021-Jun-15 at 23:55I haven't come across such a ConcurrentCounter
library, but crates.io is huge, maybe you find something. However, if you are mostly concerned with primitives such as i32
, there is a better alternative call: Atomics, definitely worth checking out.
Nevertheless, your approach of generalizing the ConcurrentCounter
is going in a good direction. In the context of operation overloading, std::ops
is worth a look. Specifically, you need Add
, Sub
, and Mul
, respectively. Also, you need a Copy
bound (alternatively, a Clone
would also do). So you were pretty close:
QUESTION
I am new to rust and I was reading up on using futures
and async / await
in rust, and built a simple tcp server using it. I then decided to write a quick benchmark, by sending requests to the server at a constant rate, but I am having some strange issues.
The below code should send a request every 0.001 seconds, and it does, except the program reports strange run times. This is the output:
...ANSWER
Answered 2021-Jun-15 at 20:06You are not measuring the elapsed time correctly:
total_send_time
measures the duration of thespawn()
call, but as the actual task is executed asynchronously,start_in.elapsed()
does not give you any information about how much time the task actually takes.The
ran in
time, as measured bystart.elapsed()
is also not useful at all. As you are using blocking sleep operation, you are just measuring how much time your app has spent in thestd::thread::sleep()
Last but not least, your
time_to_sleep
calculation is completely incorrect, because of the issue mentioned in point 1.
QUESTION
Consider the following code:
...ANSWER
Answered 2021-Jun-15 at 18:22i think you are looking for this:
QUESTION
I have a custom slide toggle component created using Angular Material. I followed this guide: https://material.angular.io/guide/creating-a-custom-form-field-control
Everything seems to be working fine except when I dynamically disable the custom component like this:
...ANSWER
Answered 2021-Jun-11 at 19:49You need to add a formGroup binding to your custom component,
QUESTION
I need a trait that allows me to construct a object that borrows an object that borrows something. In the following example that is PaperBin. https://play.rust-lang.org/?version=stable&mode=debug&edition=2018&gist=78fb3f88b71bc226614912001ceca65b
...ANSWER
Answered 2021-Jun-15 at 13:38Your immediate issue is that T: GarbageBin<'a, 'b>
where 'a
and 'b
are parameters of create_bin_with_rubbish
and must therefore outlive calls to that function—but the actual lifetimes passed to T::new
are only internal to the function and do not therefore satisfy those bounds.
Instead of parameterising create_bin_with_rubbish
with lifetimes 'a
and 'b
, one way to resolve this would be to use instead an HRTB (higher-ranked trait bound):
QUESTION
I want a function that takes two arguments, both of which can be turned into an iterator of Foo
. The snag is that I'd like to accept things which are both IntoIterator
and also IntoIterator<&Foo>
. Importantly Foo
is Copy
so I can cheaply create an owned copy from it's reference.
The solution I currently have is:
...ANSWER
Answered 2021-Jun-15 at 12:22First of all, you don't need exactly IntoIterator
bound here. It's just enough for Iterator
.
QUESTION
I was wondering if i could return a Vec<&str>
type from to_lowercase()
below?
Here is my code:
...ANSWER
Answered 2021-Jun-15 at 11:42This is not possible. The reason is that converting a Unicode String to lowercase/uppercase may need to reallocate the String, as case folding within Unicode might need more/fewer characters and/or bytes to encode the folded variant.
Either you can return a Vec
, where the new String
holds the conversion. Or, if you are sure that your input is pure ASCII, you take use make_ascii_lowercase
to do the conversion in-place; this has the downside that if proper Unicode folding requires more/less characters/bytes, no folding takes place.
QUESTION
I was looking at the Microsoft Rust guide and while reading the generics chapters, I came across the following problem.
Consider the two following pieces of code:
...ANSWER
Answered 2021-Jun-14 at 12:47In the first case:
QUESTION
I'm implementing a simple task queue using redis in Rust, but am struggling to deserialize the returned values from redis into my custom types.
In total I thought of 3 approches:
- Deserializing using serde-redis
- Manually implementing the
FromRedisValue
trait - Serializing to String using serde-json > sending as string > then deserializing from string
The 3rd approach worked but feels artificial. I'd like to figure out either 1 or 2, both of which I'm failing at.
Approach 1 - serde-redisI have a simple Task definition:
...ANSWER
Answered 2021-Jun-15 at 09:55Redis doesn't define structured serialization formats. It mostly store strings and integers. So you have to choose or define your format for your struct.
A popular one is JSON, as you noticed, but if you just want to (de)serialize simple pairs of (id, description), it's not very readable nor convenient.
In such a case, you can define your own format, for example the id and the description with a dash in between:
QUESTION
I have the following event which prevents spamming in discord and automatically mutes spammer. I took that code from a YouTube video. Here's the code:
...ANSWER
Answered 2021-Jun-14 at 16:27You need to fetch a certain amount of messages and filter it so you're only getting messages sent by the spammer then pass them to bulkDelete()
Here is a little example:
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