string::getline() and null lines

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2 total messages Started by Art Kaufmann Fri, 17 Nov 1995 23:18

#2612

Author: Art Kaufmann
Date: Fri, 17 Nov 1995 23:18

32 lines
2077 bytes

The following is an excerpt from the April WP, p 21-25, section
31.1.1.10.8:
  -- c == delim for the next available input character c(in which case the
     input character is extracted from is, but not appended to str).
     If the function appends no characters, it calls is.setstate(failbit),
     which may throw ios_base::failure(27.4.4.3).

My question is: Why indicate a failure when no characters are appended?  This
means that string::getline() cannot be used in a situation where you may get
a null line (two consecutive delim characters), since there is no way to
differentiate between this kind of "failure" and something more serious.

The definition of failure (p 27-13, Table 69-iostate effects) is "that an
input operation failed to read the expected characters, or that an
output operation failed to generate the desired characters."  I "expect"
getline() to read from 0 to npos-1 characters, not 1 to npos-1, as the
former is _far_ more useful to me.

Cheers,
  Art

---
Art Kaufmann                | 
afk@ElSegundoCA.ATTGIS.COM  |
--------------------------------------------------------------------------------
"... and should anyone actually read this drivel, any knowlege of your actions
will be denied by AT&T Global Information Solutions"


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Re: string::getline() and null lines

#2635

Author: Steve Clamage
Date: Sat, 18 Nov 1995 03:18

21 lines
1487 bytes

Art Kaufmann <afk@elsegundoca.attgis.com> writes:

>The following is an excerpt from the April WP, p 21-25, section
>21.1.1.10.8:
>  -- c == delim for the next available input character c(in which case the
>     input character is extracted from is, but not appended to str).
>     If the function appends no characters, it calls is.setstate(failbit),
>     which may throw ios_base::failure(27.4.4.3).

>My question is: Why indicate a failure when no characters are appended?

The wording has been modified in the September draft to say an error
is indicated when no characters have been *extracted*.


--
Steve Clamage, stephen.clamage@eng.sun.com
---
[ comp.std.c++ is moderated.  Submission address: std-c++@ncar.ucar.edu.
  Contact address: std-c++-request@ncar.ucar.edu.  The moderation policy
  is summarized in http://dogbert.lbl.gov/~matt/std-c++/policy.html. ]

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