more no_std support

[zendurix]

Although itertools have no_std support it lacks implementations of most usfeful functions like collect_vec, sorted_by() etc in no_std mode. From my tests it seems that implementing it should be fairly easy, and I will try to contribute with solution.

[jswrenn]

What do you have in mind? Vec is not available in #[no_std] contexts.

[zendurix]

So add alloc as dependency while in no_std. Most programs that use no_std already use alloc

[zendurix]

This will require adding new feature no_std so alloc can be included only there, and change
#[cfg(not(feature = "use_std"))] to #[cfg(feature = "no_std")]

[jacobrosenthal]

I can assure you that most no_std programs do not use alloc

…

On Thu, Aug 20, 2020 at 3:11 PM Michał Majda ***@***.***> wrote: This will require adding new feature no_std so alloc can be included only there, and change #[cfg(not(feature = "use_std"))] to #[cfg(feature = "no_std")] — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub <#470 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AADPI5FCBIJTTVLV4QPNI5TSBWNQBANCNFSM4QGUL6IQ> .

[zendurix]

Still I think alloc is most reasonable option here, however I am still a beginner so I don't know other good options.

[jswrenn]

This will require adding new feature no_std so alloc can be included only there, and change
#[cfg(not(feature = "use_std"))] to #[cfg(feature = "no_std")]

That doesn't sound quite right to me. Crate features should add functionality, not remove it.

A better approach would be to add a use_alloc feature and change this line to:

use_std = ["use_alloc"]

...and to change this line to:

default = ["use_alloc"]

(I don't think we currently use any std-only features, so this won't be a breaking change.)

@zendurix Are you actually programming in an environment that has alloc but not std?

[zendurix]

I am working on adding no_std feature to project, and I am already using alloc there. I think tomorrow (at my time) I will try to add and test this feature and if it works fine I will make PR.
use_alloc feature sounds good, even nalgebra has feature alloc and propably many more

[zendurix]

I think default should stay like this:
default = ["use_std"]
And I don't see reason to use alloc in std.
I think best option (most crates do this like this) is to use std as default and alloc as optional feature.

[zendurix]

I have made functional PR but I have accidentally used cargo fmt (because of good habbit :p). And I saw that you have this disabled. Should I restore code to previous formatting? (It have to be manual work though :/)

[zendurix]

I have uploaded PR
#471