Re: Converting strings to numbers with full checking

From:

red floyd <redfloyd@gmail.com>

Newsgroups:

comp.lang.c++.moderated

Date:

Tue, 15 Sep 2009 20:06:15 CST

Message-ID:

<d316f1d0-3031-457b-910a-2cbd1ec6c942@m11g2000vbl.googlegroups.com>

On Sep 15, 1:35 pm, "Martin T." <0xCDCDC...@gmx.at> wrote:

Hi all.

I'm working with Visual Studio 2005 and I'm wondering if there is
actually a proper method of converting strings to numeric types where I
would like to check that the input string is actually fully convertible
to a specific numeric type.

My requirements would be (locale and number format issues aside):
"-1" => int ... OK
"-1" => unsigned int ... FAIL (not unsigned)
"65535" => unsigned short ... OK
"65536" => unsigned short ... FAIL (overflow)
"65535" => short ... FAIL (overflow)
"18446744073709551615" => unsigned __int64 ... OK
"18446744073709551616" => unsigned __int64 ... FAIL (overflow)
"18446744073709551615" => __int64 ... FAIL (overflow)

All following comments apply to VS2005:
atoi() + errno - Failure to convert cannot be distinguished from zero.

strtol() + errno - Failure to convert cannot be distinguished from zero.

sscanf() - unsigned int doesn't work ("-100" will be converted with %u)

boost::lexical_cast - same problems as above, as under the hood the same
conversion routines will be used for C++ streaming.

strtol() + errno should. The second argument to strtol(), if non-
null, gives a pointer to the character past the converted string.

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