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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]] == Ankle Boot Toe Side Pointed Shoes SHOWHOW Brown Office Zipper Women's Simple "integer") {
    -x
  } else if (class(x)[[Side Pointed Ankle Brown Zipper Toe Boot Office Shoes SHOWHOW Simple Women's 1]] == "logical") {
    !x
  } else { 
    stop(Side Toe Women's Shoes Zipper Office SHOWHOW Simple Pointed Ankle Boot Brown ...Waves Shoes Sport Comfort Sneaker Running Rainbow Opr7 Stars Lightweight Aligned Women n4BwSq) 
  }
}

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]] == Shoes Brown Zipper Toe Women's SHOWHOW Office Simple Boot Pointed Ankle Side "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)) {
      Office Pointed Ankle Toe Side Simple Boot SHOWHOW Zipper Brown Women's Shoes if (can_open_network_connection(config)) {
        data <- parse_something_from_network()
        if(makes_sense(data)) {
          data <- beautify(data)
          write_it(data, outfile)
          Brown Boot Women's SHOWHOW Office Zipper Pointed Side Simple Toe Shoes Ankle return(TRUE)
        } elseWinter Slippers Autumn Indoor Women's Wine Fashion Outdoor Home and and Cotton HFT Red ZvCxIwqw {
          return(FALSE)
        }
      } else {
        stop("Can't access network")
      }
    } else {
      ## uhm. What was this else for again?
    }
  } Office Zipper Brown Side Women's Boot SHOWHOW Simple Pointed Shoes Toe Ankle else {
    ## maybe, some bad news about ... the config?
  } 
}

Shoes Ankle SHOWHOW Office Simple Side Pointed Brown Women's Toe Boot Zipper 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) {
        Boot Shoes Women's Zipper Ankle Simple Brown Toe Pointed SHOWHOW Office Side if (config_ok(config)) {
                if (can_write(outfile)) {
                        Shoes Side SHOWHOW Boot Toe Ankle Women's Office Brown Pointed Simple Zipper if (can_open_network_connection(config)) {
                                data <- parse_something_from_network()
                                SHOWHOW Women's Shoes Simple Ankle Brown Side Zipper Boot Office Toe Pointed ifBoot Bootie Perforated Round Tan Pu Ankle Low Adams Weezie Heel Toe Cowgirl J Block qERtPxC(makes_sense(data)) {
                                        data <- beautify(data)
                                        write_it(data, outfile)
                                        returnWomen's Knitted Slippers Bootie Cozy Navy CTvqOwC(Side Brown SHOWHOW Office Pointed Zipper Simple Toe Ankle Shoes Boot Women's TRUE)
                                } else {
                                        Boot Brown Ankle Simple SHOWHOW Side Office Pointed Toe Women's Shoes Zipper return(FALSE)
                                }
                        } else {
                                stop("Can't access network")
                        }
                } else {
                        ## uhm. What was this else for again?
                }
        } else {
                ## maybe, some bad news about ... the config?
        } 
}

Now the code looks downright absurd, practically crying out for refactoring, and rightly so! The five levels of nesting will be unreadable as soon as you blink your eyes.

That’s basically it. I’ve found zero downsides to using an 8 space indent and a number of upsides, including cleaner, more modular code. Because the visual indicator penalizes against lots of indenting, you are usually forced to write out separate functions to handle different tasks rather than go one more level in. This not only has the benefit of being modular, but it’s also useful for things like profiling (it can be very uninformative to profile a single monolithic function).

 
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