Code formatting edge-cases


I usually have a good idea of how I like my code to look so I can parse it in the future, but sometimes I just hit a wall trying to figure out how to format some of the longest lines in my code to keep under the 100 column limit.

I know it’s okay to go over sometimes (in the words of Captain Barbosa, “They’re more like guidelines than actual rules…”) but I don’t like to because I think long solitary lines are ugly. However, I’ve been experimenting with some styles and I don’t know which of them is less ugly than just fudging the column limit.

Here’s some out-of-context snippets I’ve been most heavily tested while working on, from

Long type and parameter lists in function

Long concrete parameter list in function

Long where clause in impl, pushed left by some naivety in Rust’s associated type lookup:

Long for-loop iterator expression:

I have read the Rust style guide but it’s been a while and I haven’t been able to find an up-to-date copy online. Last time I checked, it didn’t really cover things like this. I assume they must be edge-cases.

I know the code is probably full of logic errors as well; I’m still working on it. It’s an almost-total rewrite of an old project of mine.


There’s an active discussion on an RFC: Style: function declarations, which might have some more on this.


Personally, I’d either (a) bind the expression you are looping over to a name or (b) use the foreach method from itertools.


@DroidLogician I’m pretty strict about column limits too, except I keep it to 80 columns instead of 100. If you stroll through my code, you may find some ideas. In particular:

This is a technique I use a lot if it’s too inconvenient to use line continuations. Giving names to intermediate things is sometimes nice too, for its own sake.


This is really no easy task. See below what I think is the best you can do. But I think I would too try to bind some of the subexpressions to their own variables.

for (search_idx, maybe_boundary) in
                          .filter(|&(_, window)| window[0] == boundary_0) 
    self.boundary_read = self.boundary == maybe_boundary;
    self.search_idx += search_idx;            


80 is a bit short, IMO. 100 is just about right to fit in Vim when I have it splitting the screen widthwise with an MSYS2 console.