Yihui Xie

Redundancy in "if (x == TRUE)"

Yihui Xie / 2017-09-11

Last year when I was at JSM, I attended an excellent talk by Nicholas Horton and later nitpicked his R code:

ifelse(dest == "ORD" | dest == "MDW", TRUE, FALSE)

There is no need to use ifelse() here. The code above is equivalent to:

dest == "ORD" | dest == "MDW"

I have a feeling that some people are not comfortable when they think about Boolean values without literally seeing the values TRUE or FALSE. I think this is understandable. Personally I try to avoid redundancy, unless I’m explicitly thinking of the Department of Redundancy Department.

I also often see people write code like if (x == TRUE). The == TRUE part is redundant in my eyes: if (x) is enough. I think there is a slight visual benefit of explicitly comparing x with TRUE, though. That is, when glancing at the code, you can quickly know there is a Boolean comparison here, because the keyword TRUE is visually prominent.

A few minutes ago I saw yet another example of redundancy in the article “Flawed code served as icing on the cake for Prime Minister’s social agency launch”. The last line of the R code on the cake was like:

minister_greeting = ifelse(welcomeSpeech == TRUE, "....")

This line was quite interesting in several aspects:

  1. It is flawed because the third argument of the ifelse() function was missing (with no default).

  2. Again, there is redundancy in welcomeSpeech == TRUE: ifelse(welcomeSpeech) suffices. However, I think this redundancy is understandable since the cake is for someone who (I assume) do not really know much about R, and ifelse(welcomeSpeech == TRUE) may make the code a little more readable to them.

  3. The author of this piece of code used the left arrow <- for assignments on all previous lines, but changed to the equal sign = on the last line. As you all probably know, I use the euqal sign all the time (except when I collaborate with someone who insists on using the arrow), so I’d like to say “Welcome to the dark side and long live the equal sign!”

  4. Similarly, the author used snake_case everywhere, and suddenly changed to camelCase when naming the variable welcomeSpeech. Consistency is hard.