[J3] [EXTERNAL] [BULK] Re: A couple more ideas for features

Holcomb, Katherine A (kah3f) kah3f at virginia.edu
Thu Apr 6 15:24:55 UTC 2023

As already noted, do while (.not. cond) is not equivalent to a repeat until, since it will not execute if .not. cond starts as F whereas a repeat until cond will execute at least once regardless of the initial value of the conditional.  Sometimes that behavior is desirable.

The equivalent would be like C++
while (cond)
To my knowledge, Fortran doesn’t support this  (?)

Katherine Holcomb
UVA Research Computing  https://www.rc.virginia.edu
kah3f at virginia.edu<mailto:kah3f at virginia.edu>    434-982-5948
From: J3 <j3-bounces at mailman.j3-fortran.org> On Behalf Of Clune, Thomas L. (GSFC-6101) via J3
Sent: Thursday, April 6, 2023 11:11 AM
To: David Muxworthy <d.muxworthy at bcs.org.uk>; General J3 interest list <j3 at mailman.j3-fortran.org>
Cc: Clune, Thomas L. (GSFC-6101) <thomas.l.clune at nasa.gov>; d.muxworthy at icloud.com
Subject: Re: [J3] [EXTERNAL] [BULK] Re: A couple more ideas for features

Hi David,

EXIT and CYCLE definitely make DO WHILE unnecessary; no argument there.   But I have many cases where I consider DO WHILE(cond) to make the loop more intelligible to humans.  My guess is that there are far fewer cases where DO … UNTIL provides such additional clarity.


  *   Tom

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Subject: [EXTERNAL] [BULK] Re: [J3] A couple more ideas for features

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The DO block was introduced in F90.  As I remember the discussions, it was thought that DO ... END DO with EXIT and CYCLE made WHILE and UNTIL unnecessary.  However WHILE got added because other languages had it.


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