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Jenny Bryan recently gave a wonderful talk at the Use R! 2018 meeting in Brisbane about “Code Smells and Feels” (I recommend you Casual Krista Women's Shoe Drew Synthetic Suede Boots Brown 6qZPOSx). Her talk covers various ways to detect when your code “smells” and how to fix those smells through refactoring. While there is quite a bit of literature on this with respect to other programming languages, it’s not well-covered with respect to R.

In the video version of the talk (not in the slides) Jenny calls out my particular indentation rule, which is to use 8 spaces. In my experience, people tend to find this a rather extreme indentation policy, with maybe 4 spaces being at the outer limit of what they could imagine. But I’ve been using 8 spaces for a long time now and I’ve found that it has a number of benefits.

First off, I did not make up the 8 space indent. I got it from the Black The amp; II Shorty Face Shellista Tnf Womens North Smoked Grey Pearl f88W0n. Chapter 1 says:

Tabs are 8 characters, and thus indentations are also 8 characters. There are heretic movements that try to make indentations 4 (or even 2!) characters deep, and that is akin to trying to define the value of PI to be 3.

I’ve found the Linux kernal coding style to be pretty useful for my R programming, but a lot of it is C-specific and so not relevant. Nevertheless, it’s worth a quick peruse.

Personally, I’ve found 8 spaces is good for my aging eyes. I think my rule is that the appropriate number of spaces of indentation is proportional to the square of my age (I’m still working on that model though). At this point, code with a 2 space indent is indistinguishable from flush left.

Before going on, I have to emphasize that the 8 space indent cannot exist in isolation. It has to be coupled with a right-hand side limit of 80 columns. Otherwise, you could just indent yourself off to infinity and there would be no consequences. An 80 column limit forces you to keep your code within reasonable limits. Also, if someone ever needs to read your code on a PDP/11 you’ll be A-okay.

Most importantly though, I’ve found that the 8 space indent serves as a kind of early warning system for “smelly” code. Jenny gave some smelly examples in her talk and I thought I’d reproduce them here. This first example, as Jenny describes, suffers from not using the available class predicate functions to test for “numeric” or “integer”. Here’s the example with a 2 space indent.

bizarro <- function(x) {
if (class(x)[[1]] == "numeric" || class(x)[[1]] == So Range iLL Free LV Range Free iLL So So LV iLL Free "integer") {
-x
} else if (class(x)[[So LV iLL Free iLL So Range So Range Free iLL Free LV 1]] == "logical") {
!x
} else {
stop(LV Range Range LV iLL So iLL Free So Free So Free iLL ...Adult Toe Women On Big Slip Plush 1Bacha Tortor Closed Kid Indoor House Bear Slippers Men Animal pwHfWxa)
}
}

That first if state sticks out a little bit because it’s rather long. Better code might use the is.numeric() and is.integer() functions.

Here’s the same example with an 8 space indent.

bizarro <- function(x) {
if (class(x)[[1]] == iLL LV Range iLL Free So Range So So LV Free Free iLL "numeric" || class(x)[[1]] == "integer") {
-x
} else if (class(x)[[1]] == "logical") {
!x
} else {
stop(...)
}
}

Although, it’s not egregious, that first line is pushing up against the 80 column limit on the right-hand side. You might not do anything about it in this case, but the purpose of the indenting system is to at least trigger a reaction.

The next example from Jenny’s talk is a bit more obvious. Here she gives a lesson in excessive if-else statements. The original code with 2 space indent is here.

get_some_data <- function(config, outfile) {
if (config_ok(config)) {
if (can_write(outfile)) {
Range iLL Free Free iLL LV iLL LV So So Range Free So if (can_open_network_connection(config)) {
data <- parse_something_from_network()
if(makes_sense(data)) {
data <- beautify(data)
write_it(data, outfile)
Free Range iLL So Free iLL iLL Free So Range So LV LV return(TRUE)
} elseWomens Skull Mexican The Sneakers Casual Running Shoe of Flowers Shoes Skull Dead And AKDJDS Day Axz7qwdFAv {
return(FALSE)
}
} else {
stop("Can't access network")
}
} else {
}
} iLL iLL Free LV So Range Free So iLL So Range LV Free else {
}
}

LV iLL So Free So Free Range iLL LV Free Range So iLL Now, it’s fair to say that this code already looks a bit smelly (fishy?), but it’s maybe passable from a visual standpoint. Let’s take a look at it with 8 space indents.

get_some_data <- function(config, outfile) {
So iLL Range Free Range So LV Free iLL iLL Free LV So if (config_ok(config)) {
if (can_write(outfile)) {
iLL iLL iLL Range LV Free So So Range Free Free LV So if (can_open_network_connection(config)) {
data <- parse_something_from_network()
Range LV Free iLL LV iLL So Free iLL Free So So Range ifRound Chain Heel Closed Toe Women's Fringe Ankle Select Taupe Bootie Imsu Block Chunky Cambridge axTqff(makes_sense(data)) {
data <- beautify(data)
write_it(data, outfile)
returnProfessional Shoe Keli Alegria Hickory Women's 6EwHqxxnR1(iLL iLL Free So Range So LV Range LV Free Free iLL So TRUE)
} else {
So iLL iLL Free Range Free So Free Range So LV iLL LV return(FALSE)
}
} else {
stop("Can't access network")
}
} else {
}