Every time I use the function stopifnot(...), I have to stop and think about it: should the conditions in ... return TRUE or FALSE? Then I have to think in plain English. Hmm, what does “stop if not false” mean? Do I actually want to stop or not if the condition is true? All kinds of circles emerging in my mind…
I have wished many times the function name were stopif() instead. Reasoning about negations is often trickier than affirmatives. Compare these examples:
stopifnot(x == 1)
stopifnot(x != 1)
stopif(x == 1)
stopif(x != 1)
To me, the stopif() versions are much clearer (stopif(x) means if (x) stop(), and stopifnot(x) means if (!x) stop()). That was one of the minor reasons why I created the testit package and wrote the assert() function. When you assert(), you must assert something is true.
library(testit)
assert(1.0 == 1)
assert('1.0 is equal to 1', {
(1.0 == 1)
})
This morning I opened the help page ?installed.packages, and saw the argument noCache = FALSE. It was not the first time I had read this help page, but…
noCache = FALSE? Excuse me. I’m slow. Just give me five seconds to decipher it again.
Strunk and White actually recommended in The Elements of Style that “we put statements in positive form”, which I believe also applies to program code.
Well, if you look at ?download.file, there is an argument cacheOK = TRUE. Sigh… Why the name cacheOK? Why not just cache = TRUE? cacheOK = TRUE reads like “the statement ‘it is okay to use cache’ is okay”. Double affirmatives this time?
Once again: naming, is, hard.
Donate
As a freelancer (currently working as a contractor) and a dad of three kids, I truly appreciate your donation to support my writing and open-source software development! Your contribution helps me cope with financial uncertainty better, so I can spend more time on producing high-quality content and software. You can make a donation through methods below.
-
Venmo:
@yihui_xie, or Zelle:xie@yihui.name -
Paypal
-
If you have a Paypal account, you can follow the link https://paypal.me/YihuiXie or find me on Paypal via my email
xie@yihui.name. Please choose the payment type as “Family and Friends” (instead of “Goods and Services”) to avoid extra fees. -
If you don’t have Paypal, you may donate through this link via your debit or credit card. Paypal will charge a fee on my side.
-
-
Other ways:
WeChat Pay (微信支付：谢益辉) Alipay (支付宝：谢益辉) 
When sending money, please be sure to add a note “gift” or “donation” if possible, so it won’t be treated as my taxable income but a genuine gift. Needless to say, donation is completely voluntary and I appreciate any amount you can give.
Please feel free to email me if you prefer a different way to give. Thank you very much!
I’ll give back a significant portion of the donations to the open-source community and charities. For the record, I received about $30,000 in total (before tax) in 2024-25, and gave back about $15,000 (after tax).