From jkr@jkr.cc.rl.ac.uk Mon May 14 14:59:25 2001 Received: from nameserv.rl.ac.uk (nameserv.rl.ac.uk [130.246.135.129]) by dkuug.dk (8.9.2/8.9.2) with ESMTP id OAA39774 for ; Mon, 14 May 2001 14:59:16 +0200 (CEST) (envelope-from jkr@jkr.cc.rl.ac.uk) Received: from jkr.cc.rl.ac.uk (jkr.cc.rl.ac.uk [130.246.8.20]) by nameserv.rl.ac.uk (8.8.8/8.8.8) with ESMTP id NAA02604 for ; Mon, 14 May 2001 13:59:29 +0100 Received: (from jkr@localhost) by jkr.cc.rl.ac.uk (8.8.8+Sun/8.8.8) id OAA13088 for SC22WG5@dkuug.dk; Mon, 14 May 2001 14:01:37 +0100 (BST) Date: Mon, 14 May 2001 14:01:37 +0100 (BST) From: John Reid Message-Id: <200105141301.OAA13088@jkr.cc.rl.ac.uk> To: SC22WG5@dkuug.dk Subject: Interp F90/191 MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" WG5, Here is a draft response for interp. F90/191. Comments, please, preferably to me in private, before I send this to J3. John Reid. J3/01-xxx Date: 2 May 2001 To: J3 From: John Reid Subject: Interpretation F90/000191 (Interaction of SEQUENCE derived types and rename) Here is a new draft response. I append the present draft and the comments on it that were made with the J3 ballot in 1995. I have based this draft reply on the suggestion that I made in my 1995 ballot comment. NUMBER: F90/000191 TITLE: Interaction of SEQUENCE derived types and rename KEYWORDS: SEQUENCE, derived type, use association, derived type DEFECT TYPE: Interpretation STATUS: J3 consideration in progress QUESTION: Consider the following: MODULE M TYPE T SEQUENCE TYPE (T), POINTER :: P END TYPE END MODULE USE M, T2=>T TYPE T SEQUENCE TYPE (T2), POINTER :: P END TYPE TYPE (T) X TYPE (T2) Y X = Y END Section 4.4.2, 'Determination of derived types', seems to indicate that types T and T2 in the main program refer to the same type. Note that both types have structure components that agree in order, name, and attributes. However, considering type T in the context of module M only, type T is a derived type that contains one component that is a pointer to itself. In the context of the main program, type T is a derived type that contains one component that is a pointer to a different derived type. Are types T and T2 considered to be the same type? ANSWER: Yes, T and T2 are the same type. DISCUSSION: By the use of rename, it is possible for a scoping unit to have access by different local names to two separate derived-type definitions that have the same original name. Section 4.4.2 says: 'Data entities in different scoping units also have the same type if they are declared with reference to different derived-type definitions that have the same name,... '. This wording makes clear that it is the name of the derived-type definition (the original name) that is crucial when deciding whether two types are the same, rather than the local name of the type. This is confirmed in NOTE 4.32. EDITS: None. SUBMITTED BY: Janice C. Shepherd HISTORY: 94-273 m130 submitted 94-377 m131 Response submitted, approved u.c. 95-034r1 m132 X3J3 ballot failed 15-5 ----------------------------------------------------------------------------- Old answer ANSWER: Yes, T and T2 are the same type. An edit is provided to clarify this conclusion. Discussion: The first sentence in section 4.4.2 states, "a particular type name may be defined at once in a scoping unit." However, by the use of rename, it's possible for a scoping to have access to two separately defined derived types, that were originally defined the same name, by two different local names. For derived types made accessible by use association, the derived type name referred to in section 4.4.2 is in the corresponding . Edits are provided to clarify this. EDITS: 1. In section 4.4.2, add the following to the end of the first paragraph: [35:39] "In addition, two derived types accessible in the same scope might be the same if one or both are accessible by use association." 2. In section 4.4.2, after the second paragraph, add the following independent paragraph: [35:46] "Note that the criterion that the two types have the same name applies to the of the respective ." ------------------------------------------------------------------------------- Ballot comments 000191 Interaction of SEQUENCE derived types and rename Vote = 15 (6) - 5 191 N Adams I feel strongly that no edits to the document are needed. An answer is all that is required. The edit to section 4.4.2 contributes to any confusion over naming and rename for derived types. 191 Y Barber In the second edit I find use of "respective" in a singular context unusual. This reads better if you change to s and to s. I realise using plural versions of syntactic class names is also awkward but I can't think of a better wording right now. 191 Y Bierman The first sentence of DISCUSSION is missing a word. Most I think. Also missing the word unit (as in scoping unit). I suspect that other changes will be proposed by others. I hope so, as it's pretty unreadable (to someone not hip to the subgroup meeting/discussions) otherwise. 191 N Dedo I agree with John Reid. 191 Y Hirchert I am voting yet because I believe the answer to be correct. I find it difficult to dispute John Reid's claim that the edits are unnecessary, since both appear to be notes, but I'm not certain that this means that they should not be made. 191 Y Levine Reid raises some valid concerns. The case is fairly complex, however, and the additional "note that" comments seems to enhance the comprehensibility. 191 N Maine Agree with John Reid's comments. I hadn't noticed interp 20 when voting on this at the meeting. 191 N martin The edits are not needed, and worse, are confusing. I recommend this item be subsumed by item 20. There are several problems in the Discussion (words and letters missing), but if it is going away, it is not worth fixing. If, instead, John Reid's answer is substituted, I believe "scoping" (in the first line of Discussion) should be "scoping unit", and in the second paragraph, "interpretation", should be "defect item". 191 N North See comments by J. Shepherd and R. Maine. 191 N Reid No edits are needed in response to this interpretation. This question is very close to that raised in 006/020 and no edits were deemed necessary then. The first edit will confuse the reader of paragraph 1, which is correct as it stands. The second edit is unnecessary because the wording in lines 41-43 is 'Data entities in different scoping units also have the same type if they are declared with reference to different derived-type definitions that have the same name,... ' This wording already makes clear that it is the name of the derived-type definition that is crucial, not the local name of the type. Here is an alternative answer: ANSWER: Yes, T and T2 are the same type. DISCUSSION: By the use of rename, it is possible for a scoping to have access by different local names to two separate derived-type definitions that have the same original name. Section 4.4.2 says: 'Data entities in different scoping units also have the same type if they are declared with reference to different derived-type definitions that have the same name,... '. This wording makes clear that it is the name of the derived-type definition (the original name) that is crucial when deciding whether two types are the same, rather than the local name of the type. See, also, the discussion in interpretation 020. REFERENCE: ISO/IEC 1539:1991, section 4.4.2. EDITS: None. 191 Y Rolison The quote in the first sentence of DISCUSSION is missing the word "most". It should read "may be defined at most once". "a scoping to" should be "a scoping unit to". What should "originally defined the same name" really say? "originally defined with the same name"? "us association" should (I think) be "use association". :-) What does "in the corresponding " refer to? The in the module? I don't think the first edit is going to help anyone that has not studied this interpretation question. How about a little clue, like: "In addition, two SEQUENCE derived types accessible in the same scope might be the same if one or both are accessible by use association and at least one of them is renamed." The edit only applies to SEQUENCE derived types, right? If they are not SEQUENCE derived types, but they have the same name, they are by definition the same type, are they not? So then we couldn't possibly have "two" nonsequence derived types, could we? Or is this somehow trying to apply to: MODULE m1 TYPE t INTEGER i END TYPE END MODULE MODULE m2 TYPE t INTEGER i END TYPE END MODULE PROGRAM test USE m1 USE m2 TYPE(t) s ... END And how would the original new edit and my suggested edit be extended to more than two types that are the same? The second edit appears to be completely content-free. What on earth does it mean? The sentence has plural "types" but singular "". 191 Y Shepherd - In the question change "one one" to "one" ------------------------------------------------------------------