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From: Jack Klein <jackklein@spamcop.net>
Newsgroups: comp.std.c++
Subject: Re: strtod
Date: Tue,  6 Mar 2001 04:03:03 GMT
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On Mon,  5 Mar 2001 16:28:53 GMT, "Mycroft Holmes"
<holmes@technologist.com> wrote in comp.std.c++:

> Two questions:
> 
> 1] is the function "double strtod(const char* strng, char ** stopchar)"
> strictly standard c++?
> 
> 2] assuming 1 is true, is it standard to "work in place" passing stopchar =
> &strng ?

As others have said, you can do this but if you do you lose one of the
valuable properties of the strto... functions.  That is the ability to
easily tell the difference between unconvertible data or an actual
text representation that evaluates to 0 (or 0.0).

Consider:

char *endptr;

char data [/*some size*/];

double d;

/* some code to get input into data */

d = strtod(data, &endptr);

if (d == 0.0)
{
   if (endptr == data)
   {
       // output invalid data entered message
   }
   else
   {
       // data actually says "0"
   }
}

If you don't keep the original pointer around, there is no way to tell
the difference.

-- 
Jack Klein
Home: http://JK-Technology.Com

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