Nathan Grigg

Strategic line breaks


I have been deep into Latex for the last little while, pounding out my thesis. It is a long process that involves a lot of editing, rearranging, and tweaking. Every time I revise another paragraph, I give thanks that I am using fast and powerful BBEdit, and not something slow and cumbersome like Word. But something has been missing.

A couple weeks ago, I read a post by Brandon Rhodes titled “One sentence per line”. He quotes the following advice from “UNIX for beginners” [PDF] by Brian Kernighan. Kerninghan is the K in AWK, so pay attention.

Start each sentence on a new line. Make lines short, and break lines at natural places, such as after commas and semicolons, rather than randomly. Since most people change documents by rewriting phrases and adding, deleting and rearranging sentences, these precautions simplify any editing you have to do later.

One common feature of Latex, HTML, Markdown, and many other markup languages is that they ignore single line feeds in the document source. Only my collaborators and I will be reading the source, so I can format it however I want. I might as well make life easy on myself.

Return policies

If line feeds do not affect the final document, when should I end a line?

On the one hand, I could press return only when necessary, for example, to end a paragraph. My document will contain long lines, but my text editor can wrap them for me. On the down side, the long lines could cause some trouble when I work from the command line, which generally won’t wrap lines intelligently. Also, programs which compare two versions of a file will usually be less helpful since they report differences on a line-by-line basis. (Using a word-by-word diff program will improve this, but the results are still inferior to a line-based diff of a file with short lines.)

On the other hand, I could wrap text using hard returns. Most editors will do this for me, so I’m not actually pressing return at the end of each line. This will result in shorter lines, which will make the text easier to read from the command line. In Latex I will get more precise error location, since Latex reports errors by the line on which they occur.

One disadvantage of hard wrapping is that it makes editing awkward. If I add one word to one line, I will end up pushing a single word down to the next line. Then my obsessiveness requires me to “reflow” the paragraph, removing line breaks and inserting new ones so that the lines are the same length. Even though most text editors automate the reflow process, making changes becomes quite tedious—edit, reflow, edit, reflow, edit, reflow, etc. Furthermore, each edit results in many lines changing, so comparing two documents is not much easier than when I soft wrap. Even worse, reflowing paragraphs often removes line breaks that I put in on purpose.

For example, if I make a change to the beginning of a paragraph that ends with the following text:

which can be found using the formula
    a^2 + b^2 = c^2 .
This is called the Pythagorean theorem.

Reflowing is often overagressive, resulting in

which can be found using the formula \begin{equation} a^2 +
b^2 = c^2 . \end{equation} This is called the Pythagorean

The reflowed text is still correct, and will produce the same output, but is much harder to read. This kind of thing is especially a problem in a Latex math document, where I am often switching back and forth between prose and structured mathematical formulas.

A better way

Kerninghan’s suggestion to end lines at natural breaks solves many of these issues. Documents will have short lines, which is helpful for when I need to work in a terminal or send parts of a document by email. Edits will generally change a small number of lines, which makes the diff tools work.

I get the added benefit of being able to rearrange sentences and phrases much more easily. For complicated technical statements, I can use newlines and even indentation to make the source easier to parse.

The disadvantage is that I now have to push the return key at the end of every line. For a simple document that won’t go through many revisions, this may not be worth it. But Kerninghan also points out that most documents require more revisions than we initially expect. For a dissertation, and probably any academic paper, it is worth the extra effort.

Old habits die hard

Even after a few days of ending my lines manually at natural breaks, I often find myself getting close to the “right margin”. Usually, there is a perfectly placed comma a few words back where I should have ended the line.

I made an AppleScript for BBEdit called “New line after punctuation” that looks for the last punctuation mark on the line and inserts a hard return immediately after it. I have it assigned to the keyboard shortcut Control+Return.

Update: I have made some changes the the AppleScript, explained in this post. The new script is posted here.