| You make a valid point: I used the word "bug" here without trying first to define it, and that led to confusion in my mind, and thus in my comment. In that comment, I used the example of programs performing an ascending sort or a descending one. While both programs would be valid, one of them, at least, would not correspond to the intent of the programmer. From an engineering perspective, that would be considered a bug. I guess an informal yet hopefully apt definition of the word bug could be "an error in the source code of a program leading to an incorrect behaviour of that program at runtime". That incorrect behaviour can take many forms: the most obvious one is the program breaking in the middle of a computation, without providing any result (a semantic bug). A second one is when the compiler will not accept the program as valid (a syntactic bug). A third one is the program producing the wrong result, as in my example (also a semantic bug). In my mind, I only considered the first 2 kinds of errors as bugs, and qualified the last as something else, perhaps for the reason that only the programmer may really know the intent behind a program's implementation. One of the goals when designing a programming language is to help reduce the occurrence of bugs. The main strategy is to turn bugs of the first kind (semantic) into bugs of the second kind (syntactic), or at least that is my understanding. Concretely, with a powerful enough type system, one may express expected properties of a program using the provided syntax, and let the compiler validate these claims using only formal rules. |