When you say “type” I’m going to assume you mean static type mostly. But I’ll talk about dynamic types shortly. A static type is a property of a portion of a program that can be statically proven (static means “without running it”). In a statically typed language, every expression has a type whether you write … Read more
JLS hunting: It is a compile-time error if a final variable is assigned to unless it is definitely unassigned (§16) immediately prior to the assignment. Quoth chapter 16: V is definitely unassigned before a catch block iff all of the following conditions hold: V is definitely unassigned after the try block. V is definitely unassigned … Read more
the C# team could have implemented this kind of functionality. Is there some philosophical reason why it isn’t supported? There’s no technical reason, and no philosophical reason. However, as I often point out, I don’t have to provide a justification for not doing a feature. Features aren’t cheap; they are extremely expensive and they must … Read more
As well, the fact that you can use assignment to slices to modify the original list, but slices are themselves copies and not views. Hmm.. that’s not quite right; although I can see how you might think that. In other languages, a slice assignment, something like: a[b:c] = d is equivalent to tmp = a.operator[](slice(b, … Read more
It appears that simplicity was the main reason. From this interview: Gosling: For me as a language designer, which I don’t really count myself as these days, what “simple” really ended up meaning was could I expect J. Random Developer to hold the spec in his head. That definition says that, for instance, Java isn’t … Read more
Strictly speaking, this is a limitation imposed by C#, most likely for convenience of syntax. A constructor has a method body, but its member entry in IL is denoted as “.ctor” and it has slightly different metadata than a normal method (In the Reflection classes, ConstructorInfo derives from MethodBase, not MethodInfo.) I don’t believe there’s … Read more
If a program is compiled you can’t change it anymore. This is wrong. In image-based systems, like Lisp (Clojure can be seen as a Lisp dialect) and Smalltalk, you can change the compiled environment. Development in such a language typically means working on a running system, adding and changing function definitions, macro definitions, parameters etc. … Read more
The documentation implies this has a few useful properties: word[:2] # The first two characters word[2:] # Everything except the first two characters Here’s a useful invariant of slice operations: s[:i] + s[i:] equals s. For non-negative indices, the length of a slice is the difference of the indices, if both are within bounds. For … Read more
You can find an authoritative answer in microsoft/TypeScript#16 (wow, an old one); it is specifically explained in this comment: That’s because of document.all […], a quirk that gets special treatment in the language for backwards compatibility. document.all == null // true document.all === null || document.all === undefined // false In the optional chaining proposal … Read more
This is a very interesting question. My day job is to study programming languages, and Lua will repay careful study. I would say that about very few other languages (perhaps Icon and CLU). Please note that it is the language as a whole, not the individual features, which makes Lua so worthy of study. Is … Read more