[Haskell-cafe] Organizing your code files

[Hécate]

I think I can provide answers to those questions, based on what I have 
seen in the ecosystem so far:

 > Why put this typeclass in this source file and not that
one?

As you may know, modules can export other modules they depend on, but I 
would advise to put the typeclass definition in its own .Class module, 
such as Control.Monad.IO.Class 
<https://hackage.haskell.org/package/base-4.15.0.0/docs/Control-Monad-IO-Class.html>.


 > Should I put all my type signatures, typeclasses and data
structures at the top? At the bottom? Should I put them in a separate
source file?

Here is the layout I have seen most used:

module
   ( export1
   , export2
   ) where

imports

data types
instances
type aliases
newtypes
instances

functions (main API)

functions (helpers)

More generally at the project level, make sure you have a tree with few 
chokepoints. I encourage you to read this article 
https://www.parsonsmatt.org/2019/11/27/keeping_compilation_fast.html.

Cheers.

PS:

 > I can read and reuse my own code 30 years from now and not have to 
think about how much I hate past me.

This is bound to happen whether or not you have a strong & enforced 
formatting style. We simply grow up as programmers with time.

Le 12/08/2021 à 00:27, Christopher Conforti a écrit :
> On Sun, 8 Aug 2021 08:50:24 +0200
> Hécate <hecate at glitchbra.in> wrote:
>
>> On my end, I make use of automated style formatters, so that this
>> kind of thing can be kept consistent during CI. I invite you not to
>> think too much about the micro-details of code styles, but rather
>> find a tool that you can configure so that your style can be enforced
>> automatically. You'll be able to spend more cycles on programme
>> development.
> Indeed, this is the direction I'm heading. However, I'm doing it by
> hand first so I can refine my methods to a point I'm satisfied with,
> and then build the automation afterwards, hopefully doing it right the
> first time. I place value on this because I plan to stick with the same
> style throughout all my code so that I can read and reuse my own code 30
> years from now and not have to think about how much I hate past me.
>
> The sort of information I'm after answers questions similar to and
> including, "Why put this typeclass in this source file and not that
> one?" and "Should I put all my type signatures, typeclasses and data
> structures at the top? At the bottom? Should I put them in a separate
> source file?"
>
> Having outside perspectives from actual people that I'm having
> conversations with will help me both learn the finer points of the
> topic (from actual programmers) and piece together a strategy I'm happy
> with.
>
> On Sun, 8 Aug 2021 08:50:24 +0200
> Hécate <hecate at glitchbra.in> wrote:
>> Note that:
>>
>>    * Type variables are made explicit, and as such I annotate even the
>>      simplest of them (with `:: Type`)
>>    * I align the separators (., => and ->)
>>    * I use stylish-haskell & hlint
>>    * If you want finer automated control, try something like Britanny.
> Your code is a pleasure to read; I shall enjoy studying it. :-)
>
>
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-- 
Hécate ✨
🐦: @TechnoEmpress
IRC: Hecate
WWW: https://glitchbra.in
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