[J3] [EXTERNAL] Re: Why is += missing?

Thu Aug 26 16:57:11 UTC 2021

While I agree that Fortran is intermediate between COBOL and raw C in terms of verbosity and clarity, my personal feeling is that it is not at the “sweet spot”.   Something like Java I think comes closer to the optimum of brevity and clarity.     (I don’t know many programming languages, so there could well be others that I would feel the same way about.)

Of course, it is rare to find a Fortran code that is anywhere near as “clear” as software ought to be.   My own code included.    If verbosity were only the worst of the sins …

From: J3 <j3-bounces at mailman.j3-fortran.org> on behalf of j3 <j3 at mailman.j3-fortran.org>
Reply-To: j3 <j3 at mailman.j3-fortran.org>
Date: Thursday, August 26, 2021 at 11:47 AM
To: j3 <j3 at mailman.j3-fortran.org>
Cc: Van Snyder <van.snyder at sbcglobal.net>
Subject: [EXTERNAL] Re: [J3] Why is += missing?

On Thu, 2021-08-26 at 12:03 +0000, Jeff Hammond via J3 wrote:
RB:

I agree with this idea.  I was thinking adding a “.” to make it like element-wise ops in Matlab might be acceptable. I am willing to add pretty much any character or character pair in order to avoid duplicating array expressions.

For those of us who don't use C every day, writing a C program, or worse maintaining one written by someody else, requires keeping one eye on the code and one on the standard or your favorite textbook.

Fortran (Formula Translator) was originally designed to be as similar to mathematics as could be done with one-dimensional notation. Most people who write Fortran programs have been exposed to algebra. It shouldn't be necessary first to master C and Matlab.

Fortran is at a sweet spot between COBOL's extreme verbosity and the gibberish your old acoustically-coupled teletype machine used to make when the phone fell out of the coupler.

Here's an example of the latter:

#include <stdio.h>
main(t,_,a)
char *a;
{
return!0<t?t<3?main(-79,-13,a+main(-87,1-_,main(-86,0,a+1)+a)):
1,t<_?main(t+1,_,a):3,main(-94,-27+t,a)&&t==2?_<13?
main(2,_+1,"%s %d %d\n"):9:16:t<0?t<-72?main(_,t,
"@n'+,#'/*{}w+/w#cdnr/+,{}r/*de}+,/*{*+,/w{%+,/w#q#n+,/#{l+,/n{n+,/+#n+,/#\
;#q#n+,/+k#;*+,/'r :'d*'3,}{w+K w'K:'+}e#';dq#'l \
q#'+d'K#!/+k#;q#'r}eKK#}w'r}eKK{nl]'/#;#q#n'){)#}w'){){nl]'/+#n';d}rw' i;# \
){nl]!/n{n#'; r{#w'r nc{nl]'/#{l,+'K {rw' iK{;[{nl]'/w#q#n'wk nw' \
iwk{KK{nl]!/w{%'l##w#' i; :{nl]'/*{q#'ld;r'}{nlwb!/*de}'c \
;;{nl'-{}rw]'/+,}##'*}#nc,',#nw]'/+kd'+e}+;#'rdq#w! nr'/ ') }+}{rl#'{n' ')#\
}'+}##(!!/")
:t<-50?_==*a?putchar(31[a]):main(-65,_,a+1):main((*a=='/')+t,_,a+1)
:0<t?main(2,2,"%s"):*a=='/'||main(0,main(-61,*a,
"!ek;dc i at bK<mailto:i at bK>'(q)-[w]*%n+r3#l,{}:\nuwloca-O;m .vpbks,fxntdCeghiry"),a+1);
}

Yes, this is a legal C program. Compile it and run it. It's actually a pleasant surprise. I dare you to reverse engineer it.

In this case, brevity is not the soul of wit.

MK:

What happens to “a += b * c” is often optimized to an FMA if the compiler flags or defaults allow ISO/IEEE violation.  You have to talk nicely to GCC to get it to do it, whereas ICC will do it at -O1 and above.

KH:

Yeah, ÷ is available on my Mac but I assume it’s Unicode.  I am not advocating for the use of special characters in Fortran, but I wanted to use it in this thread so as to not overload /= even if it’s mostly obvious what I mean.

Jeff

From:J3 <j3-bounces at mailman.j3-fortran.org> on behalf of Bader, Reinhold via J3 <j3 at mailman.j3-fortran.org>
Date: Wednesday, August 25, 2021 at 5:29 PM
To: General J3 interest list <j3 at mailman.j3-fortran.org>
Cc: Bader, Reinhold <Reinhold.Bader at lrz.de>
Subject: Re: [J3] Why is += missing?
External email: Use caution opening links or attachments

Dear all,

I think a separate syntax should be considered for these operations if they are accepted as an addition to the language. e.g.  +.=, -.= etc.
Wrt /= it is not only the semantic overlap that is an issue but also the cognitive load on the programmer (prospective newby: “why the damn has /= a different meaning than +=?”)

Also note that for a significant subset use of the associate construct allows to often write

ASSOCIATE(X => something complicated)
...
   X = X + Y
END ASSOCIATE

Regards
Reinhold

Von: J3 <j3-bounces at mailman.j3-fortran.org>Im Auftrag von Carlson, Neil via J3
Gesendet: Mittwoch, 25. August 2021 16:03
An: General J3 interest list <j3 at mailman.j3-fortran.org>
Cc: Carlson, Neil <nnc at lanl.gov>
Betreff: Re: [J3] Why is += missing?

Jeff's point here is spot on.  The point of "+=" isn't simply about convenience.  It expresses intent.  A primary purposes of a high level language is to support code that can be more easily understood and reasoned about (by a human).  If your example is "a = a + 1" then sure "+=" looks like insignificant syntactic sugar.  But in his original example one has to carefully look at both sides of the "=" to understand that the intent is to increment.  The desire to have a complete set of such operators is obviously understandable.  But it's not right that a difficulty posed by "/=" should derail them all ("perfect is the enemy of good") -- having just "+=" and "-=" would be a major improvement to the language.

Neil

________________________________
From: J3 <j3-bounces at mailman.j3-fortran.org<mailto:j3-bounces at mailman.j3-fortran.org>> on behalf of Jeff Hammond via J3 <j3 at mailman.j3-fortran.org<mailto:j3 at mailman.j3-fortran.org>>
Sent: Wednesday, August 25, 2021 7:27 AM
To: General J3 interest list
Cc: Jeff Hammond
Subject: [EXTERNAL] Re: [J3] Why is += missing?

I will argue that it is syntactic sugar in the same sense that multidimensional arrays are.  Below is the perfectly functional C code I wrote to match my Fortran years ago (because computer scientists don’t know their history).  There is no actual need for multidimensional arrays in Fortran, just the practical difficulty of not having them.

// t3(h3,h2,h1,p6,p5,p4)+=t1(p4,h1)*v2(h3,h2,p6,p5);

t3[h3+h3u*(h2+h2u*(h1+h1u*(p6+p6u*(p5+p5u*p4))))] += t1[p4+p4u*h1] * v2[h3+h3u*(h2+h2u*(p6+p6u*p5))];

I think the relative usage of +=, -=, *=, ÷=, and **= if they were added justifies the pragmatic solution of just doing += and -=, which are more likely to have hardware support anyways.

Jeff

From: J3 <j3-bounces at mailman.j3-fortran.org<mailto:j3-bounces at mailman.j3-fortran.org>> on behalf of Steve Lionel via J3 <j3 at mailman.j3-fortran.org<mailto:j3 at mailman.j3-fortran.org>>
Date: Wednesday, August 25, 2021 at 4:13 PM
To: j3 at mailman.j3-fortran.org<mailto:j3 at mailman.j3-fortran.org> <j3 at mailman.j3-fortran.org<mailto:j3 at mailman.j3-fortran.org>>
Cc: Steve Lionel <steve at stevelionel.com<mailto:steve at stevelionel.com>>
Subject: Re: [J3] Why is += missing?

External email: Use caution opening links or attachments

On 8/25/2021 8:07 AM, Jeff Hammond via J3 wrote:

After 15 years as a Fortran programmer, I am still annoyed on a daily basis about the tedium imposed on me because Fortran lacks +=.

This was considered - there were a few requests for it in the 202X survey we ran 2017-2018. I suspect it fell off the list because of 1)  it is "syntactic sugar", not adding any new capability and 2) the existing use of /= requiring some complicated exceptions. It could be done, sure, but the demand seems low. We'll soon start the process for 202Y features - feel free to put it forward then.

Steve

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