- Declare variables at the smallest possible scope, and minimize the number of variables in scope, to reduce the probability that variables are misused.
- There’s a sharp discontinuity between a function fitting on a screen, and having to scroll to see how long it is. For this physical reason we enforce a hard limit of 70 lines per function. Art is born of constraints. There are many ways to cut a wall of code into chunks of 70 lines, but only a few splits will feel right.
I remember when getting into Haskell, back in 2010: “If your function has more than 4 lines, it is wrong”. For me, that is more meaningful than the 80 character limit. Soft-wrap exists to adapt lines of any length to your own screen. However, managing the complexity of functions and code-blocks is way more important in my book.
I know you have larger functions in Haskell (especially with monads), but keeping functions within 4 lines makes it an interesting trade-off between badly-named functions and the complexity of each function.
I know when to break this rule, as do most senior programmers. However, junior programmers lack the sensitivity to make such decision. I love having a rule-of-thumb for newcomers who are not familiar with the ecosystem or programming in general.
Btw, the rest of the style guide is quite good! Except for the number of columns thing.