Just started learning Rust. On Wikipedia it says pre-alpha stable version is not recommended because the language moves fast. But is 1.0-alpha stable now to use for learning?
I wanted to install Rust using homebrew on mac, but it only has the 1.0-alpha version.
Start now, and use the nightlies as suggested by Dietrich. The biggest conceptual chunks of the language (such as lifetimes and ownership) are extremely unlikely to change between now and 1.0-beta or 1.0. The biggest "issues" you will experience will be with the standard library - what features it exposes and how. At worst, that means you have to change some code and read a changelog each time you update the compiler.
As for how to install it, homebrew has a --head option you can use to install the newest code. You may just want to download the version from the website though or use rustup.sh.
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I've built a rust toolchain using someone else's repo, and it contains
a configure line I'm not familiar with: --release-channel=nightly
After I build and install the toolchain it reports its version as:
rustc 1.57.0-nightly (f1edd0429 2021-11-29)
while the standard off the shelf install of 1.57 reports its version as:
rustc 1.57.0 (f1edd0429 2021-11-29)
What does the nightly suffix mean in this version string?
Nightly is an unstable, unfinished, experimental version of Rust.
The name comes from the fact that literally every night a new "nightly" version is automatically released from whatever happens to be in the rust-lang repository at the time.
The nightly version allows use of Rust features that are still work in progress, special unstable features that are private to the compiler or the standard library, or even features that were failed experiments and will never be available in the stable releases of the Rust language.
Nightly versions may crash, may miscompile code, may stop working at any time. There is absolutely no warranty about them. Do not use them unless you specifically want to test the latest, unfinished Rust language features.
There's one case where users may hear about "nightly" features: when they use an outdated version of the compiler.
When an old Rust version sees language features "from the future", it may ask you to enable nightly features to use the code. This is misleading. You should upgrade Rust to the latest stable version instead of using nightly.
I would like to produce an HTML / JS page with reflex-dom (only client side, frontend).
However, I use the singletons package (2.6) and it seems that it cannot be compiled with ghcjs or ghc 8.6.5 (singletons 2.5.1, broken-unpatched). Therefore, the reflex-platform solutions, reflex-stone or equivalent did not help me.
I saw that ghcjs 8.8 or 8.10 could be installed through haskell.nix, but I did not find how.
How can I do it?
Or maybe, is there a way to use GHCJS (or reflex-platform solutions) with recent packages (that need ghc 8.8 or +)?
Is there a way to use ghcjs-8.8 or 8.10 with the reflex-platform?
First of all I would like to highlight that I'm not in any way related to GHC or GHCJS projects development, just another person who encountered similar issues, so take it with a grain of salt.
Currently GHCJS supports <= 8.6.5 out of the box. There is some development going on now and we will probably see officially supported 8.10 soon.
Meanwhile you can try to build the following branches on your own risk:
8.10
8.8
The ghcjs-8.10.7 compiler is in the nixpkgs-unstable branch, so you should be able to nix-build haskell.compiler.ghcjs810. Note that after commit 41f40771488e99c914a3da5de086cf794242c6d7 something happened to make it stop building, I don't know if this has been resolved. But if you rewind to that point your build should work.
Note also that it produces very large and rather slow executables because the optimizer is disabled. Ghcjs-8.6.0.1 is more usable in this respect.
I am using alternative version numbering approach for my projects. I have encountered strange behavior by cabal and stack that does not allow me to fully enjoy benefits of this approach. Both cabal and stack enforce version to be of format Int.Int.Int, which does not cover the case of another version format I use for branches (0.x.x, 1.x.x, 1.0.x, etc).
If I have line version: 0.x.x in my .cabal file, I am getting Parse of field 'version' failed. error when running cabal build or Unable to parse cabal file {PROJECT_NAME}.cabal: NoParse "version" 5 when running stack init.
Is there a way to disable version parsing on cabal and stack commands? Is there a flag for it? Or do I have to request this kind of change (adding flags, disabling version parsing) from the developers of cabal and stack?
Why is there any parsing at all? How does it help with building a package? Does cabal or stack automatically increment build numbers on some event? If yes, where could I read more about this? How could I influence the way version numbering incrementation gets implemented in cabal and stack? I want developers of haskell packages take into account the possibility of alternative version numbering approaches.
PS. For all interested folks, I want to quickly summarize the idea behind "weird" version numbers, such as 0.x.x, 1.x.x, 1.0.x. I use the version numbers with x's to describe streamlines of development that allow code changes while such version numbers as 1.0.0, 1.1.0, 2.35.46 are used to describe frozen states of development (to be precise, they are used for released versions of software). Note that such version numbers as 0.x.0, 1.x.15, 2.x.23 are also possible (used for snapshots/builds of software) and they mean that codebase has been inherited from branches with version numbers 0.x.x, 1.x.x and 2.x.x correspondingly.
Why do I need such version numbers as 0.x.x, 1.x.x and 2.x.x at all? In brief, different number of x's mean branches of different types. For example, version number pattern N.x.x is used for support branches, while pattern N.M.x is used for release branches. Idea behind support branches is that they get created due to incompatibility of the corresponding codebases. Release branches get created due to feature freeze in corresponding codebase. For example, branches 1.0.x, 1.1.x, 1.2.x, ... get created as a result of feature freezes (or releases) in branch 1.x.x.
I know this is all confusing, but I worked hard to establish this version numbering approach and I continue working on awareness about the inconsistencies of version numbering through my presentations and other projects. This all makes sense once you think more about the pitfalls of semver approach (you can find detailed slideshare presentation on the matter following the link). But I do not want to defend it for now. For the time being, I just want cabal and stack to stop enforcing their, as I perceive them, unjustified rules to my project. Hope you can help me with that.
You can't. The version will be parsed to Version, which is:
data Version = PV0 {-# UNPACK #-} !Word64
| PV1 !Int [Int]
Stack uses Cabal as a library but has its own Version type:
newtype Version =
Version {unVersion :: Vector Word}
deriving (Eq,Ord,Typeable,Data,Generic,Store,NFData)
Neither cabal nor stack have a way to customize the parsing. You have to write your own variant of those programs if you want to use another version type. But then again, you're not winning anything at that point: neither Hackage nor Stackage will recognize your package's version.
So the 1.x.x isn't possible at the moment. You could exchange x with 99999999 or something similar to mitigate the problem. That being said, it's not clear what cabal install should then install. The 99999999 version? Or the latest stable variant?
If you can express the semantics, a discussion on the mailing list as well as a feature request might change the behaviour in the (far away) future, but for now, you either have to patch the programs yourself or use another numbering scheme.
Is there a way to disable version parsing on cabal and stack commands? Is there a flag for it?
No.
Or do I have to request this kind of change (adding flags, disabling version parsing) from the developers of cabal and stack?
You can of course ask, but there are so many outstanding issues that you are unlikely to get any traction. You will have to be very convincing -- convincing enough to overturn more than 20 years of experience that says the current versioning scheme is basically workable. Realistically, if you want this to happen you'll probably have to maintain a fork of these tools yourself, and provide an alternative place to host packages using this scheme.
Why is there any parsing at all? How does it help with building a package?
Packages specify dependencies, and for each dependency, specify what version ranges they work with. The build tools then use a constraint solver to choose a coherent set of package/version pairs to satisfy all the (transitive) dependencies. To do this, they must at a minimum be able to check whether a given version is in a given range -- which requires parsing the version number at least a little bit.
Does cabal or stack automatically increment build numbers on some event? If yes, where could I read more about this?
There is nothing automatic. But you should take a look at the Package Version Policy, which serves as a social contract between package maintainers. It lets one package maintainer say, "I am using bytestring version 0.10.0.1 and it seems to work. I'm being careful about qualifying all my bytestring imports; therefore I can specify a range like >=0.10 && <0.11 and be sure that things will just work, while giving the bytestring maintainer the ability to push security and efficiency updates to my users." without having to pore through the full documentation of bytestring and hope its maintainer had written about what his version numbers mean.
How could I influence the way version numbering incrementation gets implemented in cabal and stack?
As with your previous question about changing the way the community does things, I think modifications to the Package Versioning Policy are going to be quite difficult, especially changes as radical as you seem to be proposing here. The more radical the change, the more carefully motivated it will have to be to gain traction.
I honestly don't know what a reasonable place to take such motivation and discussion would be; perhaps the haskell-cafe mailing list or similar.
Currently I need to resort in a sparse solver for a project. However I use an old version of Eigen3 on Ubuntu 12.04 (during the thesis I avoid unnecessary updates/upgrades), which means that all the information that I find online cannot be used at the moment because of my outdated version, while the few unsupported tools of my version are very hard to use (weird compilation errors - e.g. with unsupported/Eigen/SparseExtra)
I think that I should upgrade to the last stable version, however it is very critical that I will be able to replicate the numbers of all the experiments that I got with the current outdated version. Is Eigen safe when it comes to backwards compatibility?
Eigen is also a dependency for PCL that I'm using, so I'm not sure if this complicates things. Everything is installed with apt-get. Linking to a new version of Eigen locally for experimentation is not possible, because PCL complains and expects to find Eigen installed globally (i.e. in /usr/local/include).
Eigen is source (API) and binary (ABI) backward compatible (of course, except for unsupported/*). However, the numerical results might be slightly different due to different rounding errors, but that's already the case when, e.g., enabling/disabling SSE or OpenMP.
Since Eigen is header only, it is very easy to try the newest version.
I have the Haskell Platform 2012.4 installed on Windows. I would like to try the new extensions in GHC 7.6.2. It looks like the GHC 7.6.2 x86_64 download does not include an installer and is just the binaries. What is the proper way to get the latest version installed and set as the default for building Haskell projects? Thanks.
If you download GHC itself, you just get GHC and a tiny handful of libraries. If you download the Haskell Platform, you get GHC plus a much bigger collection of libraries. However, the Haskell Platform is updated infrequently, so you'll get an older version of GHC.
If you're asking "how do I install the Haskell Platform and then make it work with a newer GHC?", then the answer is "you don't". Haskell libraries have to be compiled for the specific version of GHC you're using.
You basically have two options:
Use the Haskell Platform, together with the version of GHC that it supplies.
Use the latest GHC, and compile whatever libraries you want manually.
On Linux it's not too bad, but Haskell libraries that bind to external C code tend to be fiddly to build on Windows. (Stuff like OpenGL, zlib, etc.) Packages that are 100% vanilla Haskell code are drop-dead easy to compile on any system.
I haven't done this and I'm at work so I can't test it out, but looking at the GHC docs I would think you can use the --with-compiler=path flag to select which version of GHC to use?
See also this question, related to using cabal with multiple versions of ghc installed. I would guess that you probably want to use cabal-dev or something to sandbox this, otherwise your package database may become a mess.
EDIT: As far as a default, I think you can set that in a cabal configuration file. See the comments to the accepted answer in that question I linked.
The other answers here are great, and I wanted to add that the current best way to get the latest version of GHC installed is to look at haskell.org's installation instructions. I bounced between lots of different options before I landed there, and I think it's the best source of truth from what I can tell.
To summarize the current instructions: if you already have chocolately set up, "at an elevated command prompt, run choco install haskell-dev, followed by refreshenv."