Rust Note 2: Map and Filter

There are two things that any functional programmer will try to implement when they find out that their language of choice has lists and function literals: map and filter. Here is how you do that in Rust:

Like with many things in Rust, it's important to consider the types involved with writing these functions. Map will take a list of any type of data (in this case, a slice of borrowed references (&[T])) and return a shiny new list. Filter will take a list of borrowed references as well, and either return a list of references to references passing the predicate (any function returning a boolean value), or return a new list. Since map is returning a new list, we will make filter do that as well.

Without further adieu, here's the code for filter:

fn filter<T: Clone>(lst: &[T], function: |x: &T| -> bool) -> Vec<T>{
    let mut lVec = vec![];
    for x in lst.iter(){
        if (function(x)) { lVec.push(x.clone()); }
    }
    lVec
}

Note that whatever type you are filtering over must be a member of the Clone trait. It means that it can return something that's not a reference. So, this code will take any slice and a predicate, and return only the values for which the predicate is true.

Here is the map function:

fn map<T, U>(lst: &[T], function: |x: &T| -> U) -> Vec<U>{
    let mut lVec = vec![];
    for x in lst.iter(){
        lVec.push(function(x));
    }
    lVec
}






This doesn't need a member of Clone, because it returns a different type, as specified by the parameter "function". Function is a function literal (technically, a closure), meaning that you can give this any function that takes the type of the list and returns any other value.

Rust Note 1: Found Self in Ident Position

If you're anything like me, you know what it's like to wrestle with new technology. No documentation, no guidance, no hope. This series is an attempt to document the pitfalls of the Rust programming language. In the first quickfix, we will fix the "Found Self in Ident Position" error.

Example code:     fn rest(&self) -> self;
Fixed code:          fn rest(&self) -> Self;

Explanation
The return type is affected by the case of the letter, much like Haskell's types. In most "self in ident position" cases, you just need to swap the case.

Why Microsoft Open Sourced .NET

20:26 derive: Troll Harder

That's the response from an IRC channel chatter after the news came out about Microsoft's .NET. It left a lot of developers in shock, some in disbelief... But mainly a lot in curiosity. Obviously something provoked Microsoft, a vehemently anti-Open source entity, to Open Source .NET, but what was it? By looking into the technical, political, and commercial implications of what this means, their reasoning becomes obvious.

The announcement for the relicensing of most of the .NET stack came on April 3rd, 2014, which is exactly 5 days before the XPocolypse, Microsoft's termination of their most widely used, widely popular desktop operating system. They need to gain market leverage again, and no legal paradigm has risen to popularity quicker during XP's reign than Open Source. A lot has changed in the decade since XP, and now Microsoft is being forced to catch up to companies like Apple and Google, who learned far sooner than Microsoft that Open Source technologies have technical and managerial advantages over closed source development.

However, the motivation isn't all an act of kindness. Microsoft's watching its Empire be chipped away by community projects that recreate Microsoft functionality. The Mono project, for instance, was a (somewhat) successful attempt at an open source .NET. With Microsoft filling this niche, the only card that Mono has to play is cross-compatibility, a technical feat not far off from possibility with the .NET source code released today.


Let's follow this tangent a little bit more. This isn't a one-off thing. Open source code is part of the new .NET foundation goals. What could the future hold for other community projects similar to Mono, like, say, MingW, if the source for other development tools gets released?

Is it a positive thing that Microsoft is moving into Open Source? Absolutely. But do not confuse business strategy with kindness, for the motives for the move are clouded by the drive for market dominance in a post-XP era.

Microsoft Open Sources Key parts of .NET Stack

git clone http://www.microsoft.com/git/windows

If you've ever dreampt about being able to type that command, your dream got a little bit closer today. During Microsoft's conference today (April 3rd 2014), Microsoft announced that Roselyn, the codename of the .NET Compiler Platform, would be open sourced. To put this into layman's terms: One of the most widely developed platforms in the world now mostly uses permissive licensing. It's more than a gift, it's straight out of left field. But what does this mean for developers, consumers, and the company?

It means an increase in quality for sure. The advantages of open sourcing code as a commercial strategy have been well documented in Eric S. Raymond's "The Magic Cauldron", and now Microsoft is finally learning to follow his advice two decades after the fact. Bugs will be fixed sooner, the number of auditors for the source will skyrocket, reducing the chance of vulnerabilities and malfunctions, and innovations can be made at a much more accelerated pace than previously possible.

So, you're aware of the benefits of Microsoft's decision and want to jump in? Getting the sources for .NET (a line I thought I'd never write on this blog) is as simple a process of just typing this line:

git clone https://git01.codeplex.com/roslyn

It's hosted on Codeplex, but it wouldn't be surprising to see a github mirror appear within the week.

ReactOS Community Edition Announced

So, after a 5+ day Hype Clock, the ReactOS Project announced their (R)evolutionary new project goals with their community-based operating system. Before the goals behind it can be explained, it's important to learn what ReactOS is:

ReactOS is a clean-room reverse engineering of NT, Microsoft's kernel used in Windows. Through binary compatibility, ReactOS is attempting to create a Free (libre) operating system compatible with Windows, in particular Windows XP. After Microsoft announced the impending EOL for XP later this month, ReactOS kicked off their new marketing campaign for this community edition.

The different between the version of ReactOS that already exists and the community edition is a democratic voting system for compatibility. In a system where compatibility is the selling point, not just an added bonus, being able to gauge what your users want finagled into compatibility is of the utmost priority in the project, so this is a step in the right direction for ReactOS, in my opinion. However, I was in a way disappointed that no new technology was being brought along with this release. Hopefully the community addition is a launchpad for the more daring works that the ReactOS devs have in the work, like their proposed Thorium Core Commercial Web OS.

What does this mean for Windows XP users, who will surely be looking for a new home this April? Probably not much, despite what most of us would like to believe. Even with the hype clock, the proof of concept, and the promise for community input, the interest in ReactOS is projected to be at an all time low according to Google Analytics.

Furthermore, if a user is still on a dying system such as XP, it's probable that if they are in the ReactOS echo chamber, they're probably in Linux's as well, and their loyalty to XP through hearing about alternatives proves their resolve to resist change. And what if a Windows user were to install ReactOS, only for it to panic on their hardware?

This is an example of good marketing from the ReactOS community, and fantastic work from the ReactOS devs. I'm sure that most of us are downloading qemu or Virtualbox this very moment, priming ourselves to give the new (R)evolution project a chance. Whether or not (R)evolution works now is irrelevant. The beauty in the project is the hope that in the near future, having to dual-boot an operating system with ethical and monetary implications will be a thing of the past.

Getting started with Herbstluftwm

It's no secret that I am a fan of tiling window managers. When my workflow consists of having 5+ Windows open in one workpspace, tiling is the easiest and most logical way to do it. So, what distinguishes herbstluftwm from other Window Managers, and how does one get started with it?

What Herbstluftwm does
Herbstluftwm is a manual tiling window manager. Which means, by default it ships with one pane where windows will be placed.

When you open windows in the workspace, they will maximize the space in this master pane. How they do so depends on what kind of layout you choose.                     

However, this is not the way that herbstluftwm is meant to be used. Manual tiling is about splitting your windows into sub-panes, like a binary tree.

Each pane essentially becomes a new herbstluftwm ready to hold windows or be split down even further.

You're probably saying to yourself "Well, that sounds top! How can I get started?"

The answer is a bit more complex than I would like to admit.

Setting up Herbstluftwm
Herbstluftwm works in a peculiar way, but a way that I personally find to be one of the best design patterns on Unix. Herbstluftwm is configured completely by a client, called herbstclient, that can be called from the command line. To facilitate consistency across sessions,  herbstluftwm allows a regular BASH script to be written to bind keys, run autostart programs, etc. This is usually placed in ~/.config/herbstluftwm/autostart. To launch herbstluftwm, just make sure that your ~/.xinitrc contains "herbstluftwm -c ~/.config/herbstluftwm".-c is the flag to set the configuration file.

My autostart script looks like this: https://gist.github.com/anonymous/9893756

Now, barring the wallpaper I use, and a couple of programs that are not installed on many systems by default, it works very well. Windows+v for a horizontal split, Windows+h for a vertical one, etc. Whether or not you can even use this exact configuration, it's a good launching point for your very own herbstluftwm experience.

Rust Language Review / Predicitons

Rust is a new systems-level programming language with inspiration from Haskell, C++, and D backed by Mozilla. It has been hailed as everything from "language of the future" to "hobbyist plaything". As someone equally interested in hobbies and viability, I decided to learn Rust, with great help from #rust on irc.mozilla.org.

However, my learning experience was anything but smooth. Let me preface this by saying that I am familiar with 10+ programming languages, with at least two from every paradigm (barring logical). It obvious what snippets of other languages rust takes from, but even then it was impossible for me to write even the simplest code without asking for help in IRC.

As an educational experiment, I was trying to implement "car", a function that returns the first element of a list.

Here is an implementation of that in, say, D:
T car(T)(T[] a){ return a[0]; }
Or Haskell:
car (x:xs) = x
But what about Rust?
fn car<'a,T>(v: &'a [T]) -> &'a T { return & 'a v[0];}
Oh boy.
For a modern language, that type of syntax is frankly unacceptable. This is the part where the rust users will come out of the woodwork with their pitchforks, saying "You can't criticize it once you just started! You can't see the beauty in it!" The harsh fact of the matter is, if any beginner has to type THAT monstrosity, for something that is shorter in even Java, the language won't find wide success.

What the Rust syntax gives it is power and correctness, and those are noble goals in a programming language. They're standing on the shoulders of giants (namely Haskell) with their type system, and extending it with lifetimes, eliminating a slew of errors. But the end result is a correct program that nobody particularly wants to maintain or continue developing. It's not comfortable to work in, but it's pretty on a deeper level. So, here's the conundrum of Rust. How much usability do you want to sacrifice for functionality?

My guess is that Rust will not replace C++, but userland C in many cases. Like C, rust is a paradigm in and of itself, and it serves the same purpose that C does, but safer. But I've seen Java programmers who don't know what an interface is, Lisp programmers who don't use macros, and Haskell players ignorant to typeclasses. The beauty that makes Rust the low-level userland programming language of the future will go right over the heads of most of its prospective users.