On Friday, December 29, 2017 22:32:01 Tony via Digitalmars-d-learn wrote: > In DLang Tour:Arrays > https://tour.dlang.org/tour/en/basics/arrays > > there is: > ----------------------------------------------- > int size = 8; // run-time variable > int[] arr = new int[size]; > > The type of arr is int[], which is a slice. > ----------------------------------------------- > > In "D Slices" > https://dlang.org/d-array-article.html > > there is: > ----------------------------------------------- > int[] a; // a is a slice > ------------------------------------------------ > > Based on those two web pages it appears that the name for a > dynamic array <reference?> in D is "slice". That is, anytime you > have a dynamic array (even a null reference version) it is called > a slice. Is that correct?
No. The term "slice" is a bit overused in D, meaning a variety of things. It doesn't help that some folks dislike the official terminology. In general, a slice is a contiguous group of elements. A slice of memory would be a contiguous block of memory. A dynamic array therefore refers to a slice of memory and could be called a slice, but it's also the case that using the slice operater on a container is called slicing - e.g. rbt[] would give you a range over the container rbt, and that range is a slice of the container, but it's not an array at all. The "D Slices" article is great for explaining how things work but does not use the official terminology. Per the official terminology, T[] is a dynamic array regardless of what memory it refers to. Assuming that it's non-null, it _does_ refer to a slice of memory, and a number of folks follow the article and call T[] a slice and refer to the GC-allocated memory that a T[] usually refers to as the dynamic array, but officially, T[] is the dynamic array, and the memory it refers to has no special name. It's just a block of memory that is usually GC-allocated, but it could be malloced or be a slice of a static array or any other type of memory (since you can create a dynamic array from pointers), and its semantics don't change based on what type of memory backs it. I gather that the author chose to refer to the GC-allocated block of memory as the dynamic array because of how the term dynamic array is sometimes used elsewhere in computer science, but as far as D is concerned, T[] is a dynamic array regardless of what memory it refers to, and personally, I think that focusing on the GC-allocated memory block as being the dynamic array causes confusion when dealing with dynamic arrays that refer to non-GC-allocated memory, since the semantics are identical regardless of what memory backs the array (it's just that if the array does not refer to a slice of GC-allocated memory, the capacity is always 0, guaranteed that appending will reallocate instead of it just being a possibility), but too many folks tend to think of them as being different. A dynamic array that refers to non-GC-allocated memory is really the same thing as one that is GC-allocated except that when you slice non-GC-allocated memory to create a dynamic array, you then need to be aware of how to manage the lifetime of that memory so that no dynamic array refering to it outlives it (just like you'd have to do with a pointer to non-GC-allocated memory). But dynamic arrays never manage their own memory. It's just that the GC does the managing by default and will reallocate the memory backing a dynamic array if an operation can't be done in-place. - Jonathan M Davis