From owner-sc22wg5+sc22wg5-dom9=www.open-std.org@open-std.org Sun Feb 18 22:35:40 2024 Return-Path: X-Original-To: sc22wg5-dom9 Delivered-To: sc22wg5-dom9@www.open-std.org Received: by www.open-std.org (Postfix, from userid 521) id 03842356D0B; Sun, 18 Feb 2024 22:35:40 +0100 (CET) Delivered-To: sc22wg5@open-std.org Received: from mail-yw1-f174.google.com (mail-yw1-f174.google.com [209.85.128.174]) by www.open-std.org (Postfix) with ESMTP id 8EB69356CDB for ; Sun, 18 Feb 2024 22:35:39 +0100 (CET) Received: by mail-yw1-f174.google.com with SMTP id 00721157ae682-607f8894550so16666547b3.1 for ; Sun, 18 Feb 2024 13:35:39 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=stevelionel.com; s=google; t=1708292138; x=1708896938; darn=open-std.org; h=in-reply-to:from:references:to:content-language:subject:user-agent :mime-version:date:message-id:from:to:cc:subject:date:message-id :reply-to; bh=mJBj4bgPD6d+TFQeX1MPoUutaHDj1ws6YkjDBz5RjiQ=; b=Ug1KIMTJ3Uq8SsSLKQRqw/TNztEXhh3E1smPiJ3Ha6fyajxfC7ZT9ef1MjkpzK2hSh RYQgd3otRmY0rnlMC0AKh52+PCwY6E8+dmy6lneYHi9ZMUVzSZUJCh5l1TS3KF+wqr1/ dy8ZAP2lI5MK0bS05ECgdfLhzo8F7dVRedqWA= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1708292138; x=1708896938; h=in-reply-to:from:references:to:content-language:subject:user-agent :mime-version:date:message-id:x-gm-message-state:from:to:cc:subject :date:message-id:reply-to; bh=mJBj4bgPD6d+TFQeX1MPoUutaHDj1ws6YkjDBz5RjiQ=; b=u1SsFmKsCGZASVaAvOaI84zTddrvCXIbZk3fknk2LN6yHMWFs5Q4yaZLGQNwe4Bhgz XpS1wbwJPRK2PhzqyJfdqgyzLYsBlQpB0zem+AiFV5F/p1vHBU3v7/3NAtN9Fcmeb5HD VTzTBHtwT8YOB+1JTgmByvlMrRwk14OvoIk+GKtT4+oS04owvZ8lo+VDIkztWCiJv6Ye GaFVVz/no8bX1ZtExnPXBkQNBW1ebwKnJ6dHZFLUUZFO0uuheX2huxoyHhJiMgVivx5h Nj09Ty0LdaxFisQUGoO/mKX7tUW7XR3h46nWm8VLaVTYiyBwWhTVBGtVGSdAhY/yXdxR xIRw== X-Gm-Message-State: AOJu0YydIy7aORUbL3U4B1jOCNWHQRcZbMLA/KRGne6mAKcQ+A5UpjUf hhxJznhQ0EFhJt5CeW2zXUI9Dai9IqIxCprqjn5C4QSznf7J/i4bE5jEnJA+Z4IxlSwfehwzm7D 80lo= X-Google-Smtp-Source: AGHT+IFK3EcWq0bFz6fxfFbroG3aNyvWwLlGIGCignrzVY0Ohpcj2Juh4nycri7osRU2S5slpfpZPw== X-Received: by 2002:a81:ae4d:0:b0:607:f50f:3770 with SMTP id g13-20020a81ae4d000000b00607f50f3770mr7205484ywk.41.1708292137910; Sun, 18 Feb 2024 13:35:37 -0800 (PST) Received: from [192.168.1.203] ([216.212.3.233]) by smtp.gmail.com with ESMTPSA id d5-20020ac84e25000000b0042de98f38f3sm1940632qtw.63.2024.02.18.13.35.37 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sun, 18 Feb 2024 13:35:37 -0800 (PST) Content-Type: multipart/alternative; boundary="------------TMkiqL7hyOJtO0H9Vo7ULn7B" Message-ID: <77dd9a36-9cda-444a-a03b-7580a081cc82@stevelionel.com> Date: Sun, 18 Feb 2024 16:35:36 -0500 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [J3] [SC22WG5.6544] Why can't USE come after IMPLICIT NONE? Content-Language: en-US To: WG5 List References: <20240218203142.DE815356D03@www.open-std.org> From: Steve Lionel X-Clacks-Overhead: GNU Terry Pratchett In-Reply-To: <20240218203142.DE815356D03@www.open-std.org> Sender: owner-sc22wg5@open-std.org Precedence: bulk This is a multi-part message in MIME format. --------------TMkiqL7hyOJtO0H9Vo7ULn7B Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit This of course dates back to Fortran 90, long before I was on the committee, but perhaps it was done to prevent confusion as to whether IMPLICIT would have an effect on the USE that follows. It wouldn't, because any implicit typing is resolved when the module is compiled, thus an IMPLICIT in the host scope would not affect any use-associated entities. I see Van has made a better observation. Even if this rule were relaxed, though, it would not help you. Consider: program main implicit none real :: foo include 'mpif.h' ... I'm skeptical that having mpif.h be a use mpi would work for everyone regardless, as there wold be scoping rule differences. On 2/18/2024 3:31 PM, Jeff Hammond via J3 wrote: > Can someone explain to me why the following is illegal? Is there a risk > that someone defines implicit variables in a module and that effect > being invisible to the user? Would it not have been better to exclude > implicit variable declaration in modules? Steve --------------TMkiqL7hyOJtO0H9Vo7ULn7B Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: 7bit
This of course dates back to Fortran 90, long before I was on the committee, but perhaps it was done to prevent confusion as to whether IMPLICIT would have an effect on the USE that follows. It wouldn't, because any implicit typing is resolved when the module is compiled, thus an IMPLICIT in the host scope would not affect any use-associated entities.

I see Van has made a better observation.

Even if this rule were relaxed, though, it would not help you. Consider:

program main
implicit none
real :: foo
include 'mpif.h'
...

I'm skeptical that having mpif.h be a use mpi would work for everyone regardless, as there wold be scoping rule differences.

On 2/18/2024 3:31 PM, Jeff Hammond via J3 wrote:
Can someone explain to me why the following is illegal?  Is there a risk
 that someone defines implicit variables in a module and that effect 
being invisible to the user?  Would it not have been better to exclude 
implicit variable declaration in modules?

Steve

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