http://d.puremagic.com/issues/show_bug.cgi?id=8185
--- Comment #3 from Denis Shelomovskij <verylonglogin....@gmail.com> 2012-06-02 14:29:01 MSD --- (In reply to comment #1) > The current behavior is by design, and perfectly fine – note that `pure` in D > just means that a function doesn't access global (mutable) state. A pointer > somewhere isn't a problem either, since the caller must have obtained the > address from somewhere, and if it was indeed from global state, the calling > code couldn't be pure. OK. Looks like everything works but I don't understand how. So could you please answer the question (read this to the end). According to http://dlang.org/function.html#pure-functions > Pure functions are functions that produce the same result for the same > arguments. And my original question is > The Question: What exactly does these pure functions consider as `argument value` and as `returned value`? Illustration: --- int f(in int* p) pure; void g() { auto arr = new int[5]; auto res = f(arr.ptr); assert(res == f(arr.ptr)); assert(res == f(arr.ptr + 1)); // *p isn't changed arr[1] = 7; assert(res == f(arr.ptr)); // neither p nor *p is changed arr[0] = 7; assert(res == f(arr.ptr)); // p isn't changed } --- Which asserts must pass? The second assert is here according to http://klickverbot.at/blog/2012/05/purity-in-d/ (yes, it's "Indirections in the Return Type?" section, but sentences looks general and I think it can be treated this way): > The first essential point are addresses, respectively the definition of > equality applied when considering referential transparency. In functional > languages, the actual memory address that some value resides at is usually of > little to no importance. D being a system programming language, however, > exposes this concept. -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
