You should use factors. Yes they can be a pain, but my theory is that 90% of why they’re a pain is because in read.table and read.csv, the argument stringsAsFactors = TRUE by default (and most users miss this subtlety). I say they are useful because model fitting packages like lme4 use factors and ordered … Read more
Because I may write Foo and its friend Bar (thus there is a trust relationship). But do I trust the people who write classes that are derived from Bar? Not really. So they should not inherit friendship. Any change in the internal representation of a class will require a modification to anything that is dependent … Read more
The use of zero to start counting is actually an optimization trick from Assembly programmers. Instead of assigning 1 to the count register, they XOR’ed the register with itself, which was slightly faster in CPU cycles. This meant that counting would start with 0 and would always be up to the length of elements, excluding … Read more
I found the following resources helpful for understanding type inference, in order of increasing difficulty: Chapter 30 (Type Inference) of the freely available book PLAI, Programming Languages: Application and Interpretation, sketches unification-based type inference. The summer course Interpreting types as abstract values presents elegant evaluators, type checkers, type reconstructors and inferencers using Haskell as a … Read more
Globals are evil This is true for the global keyword as well as everything else that reaches from a local scope to the global scope (statics, singletons, registries, constants). You do not want to use them. A function call should not have to rely on anything outside, e.g. function fn() { global $foo; // never … Read more
Sometimes it is helpful to have multiple cases associated with the same code block, such as case ‘A’: case ‘B’: case ‘C’: doSomething(); break; case ‘D’: case ‘E’: doSomethingElse(); break; etc. Just an example. In my experience, usually it is bad style to “fall through” and have multiple blocks of code execute for one case, … Read more
The issue is that when you use the literal null, Java doesn’t know what type it is supposed to be. It could be a null Object, or it could be a null Object array. For a single argument it assumes the latter. You have two choices. Cast the null explicitly to Object or call the … Read more
stopifnot() You may also be interested in packages like Runit and testthat for unit testing.
In addition to the other good answers, I’ll add yet another reason why to not put C-style constness into C#. You said: we mark parameter as const in order to be sure that its state will not be changed in method. If const actually did that, that would be great. Const doesn’t do that. The … Read more
The short answer is: because the language designers decided not to. Basically, it seemed that both the .NET and Java designers did not allow multiple inheritance because they reasoned that adding MI added too much complexity to the languages while providing too little benefit. For a more fun and in-depth read, there are some articles … Read more