NetNews Usenet Archive 1992 #20/NN_1992_20.iso/spool/comp/lang/cplus/13641

Internet Message Format | 1992-09-14 | 1.8 KB

Path: sparky!uunet!mcsun!sunic!hagbard!loglule!jbn
From: [e-mail] (Johan Bengtsson)
Newsgroups: comp.lang.c++
Subject: Comma operator for stream I/O (was: Answers on a postcard...)
Message-ID: <[e-mail]>
Date: 14 Sep 92 15:26:50 GMT
References: <[e-mail]>
Organization: Telia Research AB, Aurorum 6, 951 75 Lulea, Sweden
Lines: 48
X-Newsreader: Tin 1.1 PL4

This is a side-track from the previous discussion.  Below I propose
an alternate syntax for stream I/O (futile, I know).  I'd be curious
to know what the net thinks about it.

[e-mail] (Steve Clamage) writes:
:
: Personally, I've never seen any example of code
: which was improved by using an overloaded comma (which of course
: doesn't mean there is no such code).

Since I am also in search of an example where the comma operator would be
a good choice:

Would the comma operator have been a good choice for stream I/O?
I.e. instead of the rather hard-to-read expression

  cout << "The value is " << value << endl;

you would write

  cout, "The value is", value, endl;

The precedence is just right (very low).

The comma operator could be used for input as well:

  int i; float f; char c;
  cin, i, f, c;

Finally, for iostreams, you would invoke the methods

  istream& iostream::in();
  ostream& iostream::out();

to select input or output, like this

  iostream io(...);
  io.out(), "The value is", value, endl;
  io.in(), i, f, c;

Is this technique commonly used in MI classes (base class selector methods,
to do controlled up-casting)?  Just curious...

--
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