[Haskell-cafe] Readable Haskell

Will Bush will.g.bush at gmail.com
Tue Sep 22 19:54:46 UTC 2020

> I use Haskell to do rapid prototyping of various tools we are building,
ultimately to be delivered in python.

Off topic:

Do you feel the code comes out better when you do it that way?

I'm going to share a story I've shared a couple of times, but no one really
it. I wish it was about a more real word application, but unfortunately I
haven't had the opportunity to write those in more than one language to
and contrast.

I took an intro to game programming class in college as an elective for fun
the professor had us implement this old text based game called Hunt the
Wumpus 3
times. The first time was text based, the 2nd time was 2D, and the 3rd was
3D (aside
from a semester-long group project). I remember the instructions mandating
it is sufficiently OO (object oriented). I didn't think anything of it at
time and everything seemed fine. Note we using C# at the time because later
were going to use a framework like Microsoft's XNA. I ended up using
which is based on XNA Framework. Basically it's a lower level framework
to something like Unity.

One thing that stood out to me was I was unable to reuse anything from the
based game in the 2D one because it had IO intermingled in the code and
on blocking to get input from the user. The 2D version was using a game
loop and
was more event driven. That was my first time doing anything like that and
ended up a buggy mess that barely worked right. The third time in 3D I
think I
pretty much had to start from scratch again, but I got better at the event
driven nature of the thing and it turned out ok (it worked).

Fast forward in time and I am learning Rust for fun and decide to implement
same text based game because I want to know what it feels like to program in
that language vs C#. I thought it turned out was great until I did the same
in Haskell. Still blows my mind today how that language forced me to think
things differently. If I remember right the Haskell solution was 1/3 the
(measured with tokei) (2 source files and 1 test file vs about 9 source
and 4 test files). All the IO ended up near the main function instead of
out all over the place, and it's not just concise syntax that reduced the
of code, but a simpler solution in my opinion. The game logic became just a
bunch of pure functions in a small library that moved the game from state to
state in an immutable game object.

I haven't tried it, but I imagine I would have been able to reuse the game
in a 2D game because the logic wasn't coupled to and dependent on IO

I think the purely functional nature of Haskell, especially the type
around IO effects, drove me to a better solution. It's kind of funny in
in retrospect I find it hard not to just blame myself for over-complicating
Some of that does come down to lack of experience at the time. However, I
professionally in C# and most of the code I see seems like an
zoo with IO and partial functions everywhere.

If your interested you can judge it for yourself:

    C# text based: https://github.com/willbush/hunt-the-wumpus

    C# 3D with primitive shapes:

    Rust text based: https://github.com/willbush/wump

    Haskell text based: https://github.com/willbush/hwump

I have the 2D code in a private repo because it's such a train wreck that I
didn't want anyone to see it. I really don't care anymore so I can
it if anyone reads this far and cares to see it.

I later realized the architecture I ran across is basically this:

On Tue, Sep 22, 2020 at 1:40 PM Andrew Butterfield <
Andrew.Butterfield at scss.tcd.ie> wrote:

> +1
> I am working on a project looking at formal verfication for an open-source
> real-time operating system called RTEMS - rtems.org. I use Haskell to do
> rapid prototyping of various tools we are building, ultimately to be
> delivered in
> python.
> RTEMS coding standards for both C/C++ and Python mandate a maximum line
> length of 80,
> for pretty much the reasons stated by Ben below
> Regards, Andrew
> On 21 Sep 2020, at 20:36, Ben Franksen <ben.franksen at online.de> wrote:
> Am 21.09.20 um 12:05 schrieb Ignat Insarov:
> I did not mean to imply that every Haskell programmer has or should
> have a retina screen and a high performance GPU — only that, as a
> profession, we have way better tools now than back then.
> In humanities, it is usual for there to be either a normal
> distribution or a Pareto distribution in any large enough sample of
> data. So, unlike in precise sciences, a counter-example does not
> refute a proposition. What matters is that there is a trend. And there
> is a trend associated with larger and finer displays. It dawns on even
> the most _«old school»_ people by now. See for example a letter on
> Linux Kernel Mailing List.[1]
> What you and Mr. Torvalds forget is that there is a reason why
> newspapers are written in relatively small columns. Even scientific
> papers are often printed in two column mode. Typesetting has been done
> since a few 100 years and has for the most time been an analog
> technique, so it mostly wasn't limited by available resolution. The
> point is that humans aren't good at reading text when the line length
> exceeds roughly 80 characters because when you jump from the far right
> to the far left of the text, it gets hard to correctly identify where
> the next line starts. A value of 60 is ideal for non-indented text. Thus
> considering indentation that is not too deep, say (usually) not
> exceeding 5 levels a 4 spaces makes 20 chars, which means max. line
> length is ideal at 80 and should not exceed 100 (or 90 with 2 spaces for
> indentation).
> I can view files in fullscreen mode if forced to do so by the author of
> the code but I hate it. This has nothing to do with being old-school.
> When I tile my terminal windows on my display, I can have 6 terminals
> visible at one time, and that's because I have them three wide. And I
> could still fit 80% of a fourth one side-by-side.
> Using a laptop with max. 15 inch display? How old are you? People over
> 50 years or so usually have trouble reading such small print, no matter
> how great the resolution. So (apart from the arguments above) screen
> size often limits how much text can be displayed in a readable fashion.
> Cheers
> Ben
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> Lero at TCD, Head of Software Foundations & Verification Research Group
> School of Computer Science and Statistics,
> Room G.39, O'Reilly Institute, Trinity College, University of Dublin
>                          http://www.scss.tcd.ie/Andrew.Butterfield/
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