minow@decvax.UUCP (Martin Minow) (05/05/84)
Previously, on net.lang.c, the following was stated:
1. Decus C does not support "return expression;" where the
expression is not enclosed in parentheses.
2. Decus C predates Kernighan and Ritchie, where the parentheses
were shown as optional.
3. Version 6 Unix C compilers accepted this syntax before
before of Kernighan and Ritchie.
These statements are true. However, Decus C was coded using the
Unix Version 6 reference manual, where the only valid forms for the
return statement were
return
and return ( expression )
Since the person who wrote Decus C did not have access to the
source code for Unix C, he had no way of knowing that the syntax
accepted by the compiler did not agree with the reference manual.
We have not bothered to change Decus C as we feel that we would be
legitimizing a poor programming practice. The change to the compiler,
which is very simple, is left as a exercise for the student.
Martin Minow
decvax!minowgwyn@brl-vgr.UUCP (05/08/84)
return expr; is preferable to return(expr); since the latter looks like a function call (which it is not).
smh@mit-eddie.UUCP (Steven M. Haflich) (05/10/84)
This message is empty.
toml@druxm.UUCP (05/10/84)
> From: gwyn@brl-vgr.UUCP > > return expr; > is preferable to > return(expr); > since the latter looks like a function call (which it is not). By this reasoning, we should use "while expr" instead of "while (expr)", and "if expr" instead of "if (expr)". And don't forget "switch expr" to replace "switch (expr)". My own opinion is that "return (expr)" is clearer, since it clearly distinguishes between the keyword and the parameter. I think of this as a general "thing-to-do (thing-to-do-it-with)" syntax that is consistent among C commands, functions, and macro pseudo-functions. Tom Laidig AT&T Information Systems Laboratories, Denver ...!ihnp4!druxm!toml
coltoff@burdvax.UUCP (Joel Coltoff) (05/10/84)
<< SLIME MOLD >>
Do you think that
if expr
looks better than
if(expr)
since that also looks like a function call.
I love to play devils' advocate
--
Joel Coltoff {presby,bpa,psuvax}!burdvax!coltoff
(215)648-7258gwyn@brl-vgr.ARPA (Doug Gwyn ) (05/11/84)
Yes, ( expr ) is also an expr which is why return( expr ); is legal although the definition is return expr; However, stylistically I recommend leaving unnecessary parentheses off the return expr since, as I said, they make it look like a function call. Both ways are legal and this wouldn't be an important issue except that some C compilers (apparently the DECUS C compiler) do not accept the more general form.
gwyn@brl-vgr.ARPA (Doug Gwyn ) (05/11/84)
The examples while expr etc. are silly. They are not even legal C. return expr; is.
alan@allegra.UUCP (Alan S. Driscoll) (05/11/84)
> From: gwyn@brl-vgr.ARPA (Doug Gwyn ) > Newsgroups: net.lang.c > Subject: Re: return expr and Decus-C > The examples > while expr > etc. are silly. They are not even legal C. > return expr; > is. Of course the examples aren't legal C, but that's not the point. The question is, if you are worried that return (expr); looks like a function call, why aren't you worried that while (expr) stat; also looks like a function call? (Remember that 'stat' can be the null statement.) Aren't you being just a bit inconsistent? -- Alan S. Driscoll AT&T Bell Laboratories
chris@umcp-cs.UUCP (05/14/84)
Who says ``while (expr) statement;'' looks like a function call?
If it were a function call, the statement part would be a syntax
error. (Same goes for if(), for(), etc.... Everything except
``return''. [Well, ok, ``do-while''s are a bit funky, but I try
to end them with ``} while (expr);''.])
--
In-Real-Life: Chris Torek, Univ of MD Comp Sci (301) 454-7690
UUCP: {seismo,allegra,brl-bmd}!umcp-cs!chris
CSNet: chris@umcp-cs ARPA: chris@marylandks@ecn-ee.UUCP (05/14/84)
#R:decvax:-47800:ecn-ee:13100012:000:816 ecn-ee!ks May 13 20:44:00 1984 > Of course the examples aren't legal C, but that's not the > point. The question is, if you are worried that > > return (expr); > > looks like a function call, why aren't you worried that > > while (expr) stat; > > also looks like a function call? (Remember that 'stat' > can be the null statement.) Aren't you being just a bit > inconsistent? > > -- > Alan S. Driscoll > AT&T Bell Laboratories Personally, my perferred style avoids confusion. If a keyword is followed by a '(', I seperate them by a space. Admittedly, while(expr); looks like a function call, but while (expr) ; does not. Clear style is up to the programmer. Function calls should "look" like function calls, macros should look like function calls, but "return"s should not look like function calls. Kirk Smith Purdue EE
alan@allegra.UUCP (Alan S. Driscoll) (05/14/84)
[] >From: chris@umcp-cs.UUCP >Newsgroups: net.lang.c >Subject: Re: return expr and Decus-C >Posted: Sun May 13 21:47:44 1984 >Who says ``while (expr) statement;'' looks like a function call? >If it were a function call, the statement part would be a syntax >error. You are forgetting that the body of a while statement may be empty. -- Alan S. Driscoll AT&T Bell Laboratories
gwyn@brl-vgr.ARPA (Doug Gwyn ) (05/14/84)
Sorry, folks, but the C language gives me no option on if ( cond ) stmt or while ( cond ) stmt It DOES give me the choice of whether to write return expr; or return( expr ); Given the choice, I vote against the redundant parentheses. If the rest of the language syntax were more like Algol-68 or Djikstra's then I would be happier, but short of using Bourne's macros I have no choice about that. C definitely overworks its special characters and keywords, and this adversely affects readability. (Nevertheless I would rather use C than any of the major contenders, but within its syntax one should still adopt as readable a style as the language permits.)
dyer@vaxuum.DEC (Example #22) (05/15/84)
Re: return expr and Decus-C____________________________________________________
Keywords like if, while, and switch (which use parentheses for their
arguments) have already been mentioned as non-functions that use parentheses.
I like the parentheses, and if anyone wishes to avoid confusion between func-
tions and keywords-with-parentheses, just use some whitespace!
For example:
function(arg1,arg2)
keyword (arg1,arg2)
or, if you prefer,
function( arg1 , arg2 )
keyword ( arg1 , arg2 )
The idea is that the function is "connected" to the parentheses.
<_Jym_>
: Jym Dyer : Nashua, NH : ...{allegra,decvax,ucbvax}!decwrl!rhea!vaxuum!dyer :gwyn@brl-vgr.ARPA (Doug Gwyn ) (05/15/84)
Thanks, Kirk. I too use white space differently for the different (overloaded!) uses of parentheses in C. E.g. func( param, param ); if ( cond ) stmt; while ( cond ) stmt; a = (b + c) / d; return a == b;
chris@umcp-cs.UUCP (05/16/84)
You're right, I did actually forget about null statements, but I'm
right too: in most cases,
<insert arbitrary function name> (expr) <statement> ;
would be a syntax error. Besides, I try to keep all my "while"s
with null statements as
while (expr)
;
(By the way, does anyone have an option for the "indent" program
that comes with Gosling Emacs, to make it not put null statement
";"s right up against the close parenthesis?)
--
In-Real-Life: Chris Torek, Univ of MD Comp Sci (301) 454-7690
UUCP: {seismo,allegra,brl-bmd}!umcp-cs!chris
CSNet: chris@umcp-cs ARPA: chris@marylandajs@hpfcla.UUCP (05/16/84)
> return expr; > is preferable to > return(expr); > since the latter looks like a function call (which it is not). Unless, of course, expr is more complicated than the null string, in which case parentheses are a very nice way to set it apart. But seriously... RETURN(3) Parody Systems RETURN(3) NAME return -- return from C procedure call SYNOPSIS void return (value) anytype value; DESCRIPTION This procedure never returns to the caller. Instead, it casts the given value to the procedure type of the calling procedure, without loss of size or accuracy. Then it causes the user program to continue immediately after the place where the calling procedure was itself called. The calling procedure appears to return value to its caller as a constant of the proper type, should the caller care to use it in an expression (including a simple assignment). The value parameter is optional and may be omitted. If a procedure ends without calling return() first, the operating system calls it for you with no parameters. SEE ALSO setjmp(3) BUGS Due to a bug in the compiler, this procedure can be called without placing parentheses around its parameter.
rcd@opus.UUCP (Dick Dunn) (05/16/84)
>> return expr; >> is preferable to >> return(expr); >> since the latter looks like a function call (which it is not). > >By this reasoning, we should use "while expr" instead of "while (expr)", >and "if expr" instead of "if (expr)". And don't forget "switch expr" to >replace "switch (expr)". Seems like a good idea to me. (Put down that torch! Not for C, but for another language.) After all, Pascal manages without the parens around the expr's in "if", "while", and "case" (Pascal analog of "switch"). Of course, some Pascalers are amazed that C doesn't have "then" to go with "if". (It's a little trickier to get rid of BOTH the parens around the expr in the "if" AND the "then" keyword - but it's possible. Look at the way Icon handles comparable situations.) -- ...A friend of the devil is a friend of mine. Dick Dunn {hao,ucbvax,allegra}!nbires!rcd (303) 444-5710 x3086
bobm@zinfandel.UUCP (05/16/84)
#R:decvax:-47800:zinfandel:14600019:000:446 zinfandel!bobm May 14 23:40:00 1984 > 1. Decus C does not support "return expression;" where the > expression is not enclosed in parentheses. > We have not bothered to change Decus C as we feel that we would be > legitimizing a poor programming practice. The change to the compiler, > which is very simple, is left as a exercise for the student. What's poor about writing return 0; At least it doesn't look like a function call, like return(0); does. Bob Miller
hamilton@uiucuxc.UUCP (05/16/84)
#R:decvax:-47800:uiucuxc:21000012:000:155
uiucuxc!hamilton May 16 14:39:00 1984
i prefer
return (expr);
why shouldn't a function un-call resemble a function call? i've never
gone hunting for a function named "return" by mistake.jim@ism780.UUCP (05/18/84)
#R:brl-vgr:-151400:ism780:12500008:000:410 ism780!jim May 16 19:00:00 1984 > >Who says ``while (expr) statement;'' looks like a function call? > >If it were a function call, the statement part would be a syntax > >error. > > You are forgetting that the body of a while statement may be empty. Some people can't tell the difference between a discussion and a debating club. Please restrict this sort of irrelevant drivel to net.politics. -- Jim Balter, INTERACTIVE Systems (ima!jim)