Why the first 4 character set with 0?

[cutecutemouse]

I'm writing a casting function like that,
string dbl2s(double dbl)
{
char chs[MAX_STRING_LENG TH];
memset(chs, 0, sizeof(chs));
_snprintf_s(chs , _countof(chs), MAX_STRING_LENG TH, "%f", dbl);
return string (chs);
}

------------------------------------------------------------------

I find that each time when the double value converts to the char
array. The first 4 char will be set to 0, but from the 5th one will
be the right value. So in the end the string will be treated as a null
string. I use std::string.

Does anybody know why? I really appreciate for your help.

[Victor Bazarov]

cutecutemouse wrote:

I'm writing a casting function like that,
string dbl2s(double dbl)
{
char chs[MAX_STRING_LENG TH];

I would strongly recommend initialising it:

char chs[MAX_STRING_LENG TH] = {};

then you don't need the following statement.

memset(chs, 0, sizeof(chs));
_snprintf_s(chs , _countof(chs), MAX_STRING_LENG TH, "%f", dbl);

What does that function do? What are the meanings of the second and the
third argument? You're supplying the same value, no?

return string (chs);
}

------------------------------------------------------------------

I find that each time when the double value converts to the char
array. The first 4 char will be set to 0, but from the 5th one will
be the right value. So in the end the string will be treated as a null
string. I use std::string.

Does anybody know why? I really appreciate for your help.

Since '_snprintf_s' is not a standard function, you should either
explain what it's supposed to do, or post to the newsgroup where it is
on topic.

V
--
Please remove capital 'A's when replying by e-mail
I do not respond to top-posted replies, please don't ask

[cutecutemouse]

I want to convert a double value to a string. And I read about this
function from an article. I just want to know why this problem
happened.
On 27 Jul., 16:32, Victor Bazarov <v.Abaza...@com Acast.netwrote:

cutecutemouse wrote:

I'm writing a casting function like that,

string dbl2s(double dbl)
{
char chs[MAX_STRING_LENG TH];

I would strongly recommend initialising it:

char chs[MAX_STRING_LENG TH] = {};

then you don't need the following statement.

memset(chs, 0, sizeof(chs));
_snprintf_s(chs , _countof(chs), MAX_STRING_LENG TH, "%f", dbl);

What does that function do? What are the meanings of the second and the
third argument? You're supplying the same value, no?

return string (chs);
}

------------------------------------------------------------------

I find that each time when the double value converts to the char
array. The first 4 char will be set to 0, but from the 5th one will
be the right value. So in the end the string will be treated as a null
string. I use std::string.

Does anybody know why? I really appreciate for your help.

Since '_snprintf_s' is not a standard function, you should either
explain what it's supposed to do, or post to the newsgroup where it is
on topic.

V
--
Please remove capital 'A's when replying by e-mail
I do not respond to top-posted replies, please don't ask

[Jim Langston]

"cutecutemo use" <pl******@hotma il.comwrote in message
news:f8******** *************** ***********@m45 g2000hsb.google groups.com...

On 27 Jul., 16:32, Victor Bazarov <v.Abaza...@com Acast.netwrote:

>cutecutemous e wrote:

I'm writing a casting function like that,

string dbl2s(double dbl)
{
char chs[MAX_STRING_LENG TH];

I would strongly recommend initialising it:

char chs[MAX_STRING_LENG TH] = {};

then you don't need the following statement.

memset(chs, 0, sizeof(chs));
_snprintf_s(chs , _countof(chs), MAX_STRING_LENG TH, "%f", dbl);

What does that function do? What are the meanings of the second and the
third argument? You're supplying the same value, no?

return string (chs);
}

------------------------------------------------------------------

I find that each time when the double value converts to the char
array. The first 4 char will be set to 0, but from the 5th one will
be the right value. So in the end the string will be treated as a null
string. I use std::string.

Does anybody know why? I really appreciate for your help.

Since '_snprintf_s' is not a standard function, you should either
explain what it's supposed to do, or post to the newsgroup where it is
on topic.

>I want to convert a double value to a string. And I read about this
function from an article. I just want to know why this problem
happened.

Please don't top-post, message rearranged.

I googled for _snprintf_s and found out it's Microsoft's bastardisation of
sprintf, and, yes, it seems the 2nd and 3rd parameters in this case should
be the same. Using the standard version would give us:

sprintf( chs, "%f", dbl );

which looks fine to me. To be hontest, I don't know what the problem is,
not sure if it's a Microsoft problem, something else, etc.. but afaic it
doesn't matter because _snprintf_s should never be used anyway, just use
stringstream.

std::stringstre am convert;
convert << dbl;
std::string value;
convert >value;

This kind of thing is done so much, in fact, that there are templates for
it. This is the one I use:

template<typena me T, typename F T StrmConvert( const F from )
{
std::stringstre am temp;
temp << from;
T to = T();
temp >to;
return to;
}

template<typena me Fstd::string StrmConvert( const F from )
{
return StrmConvert<std ::string>( from );
}

If you use boost they have a lexical cast that's about the same thing.
Anyway, it's rather simple.

double Foo = 1234.56;
std:::string Bar = StrmConvert( Foo );

[Daniel T.]

cutecutemouse <pl******@hotma il.comwrote:

I'm writing a casting function like that,
string dbl2s(double dbl)
{
char chs[MAX_STRING_LENG TH];
memset(chs, 0, sizeof(chs));
_snprintf_s(chs , _countof(chs), MAX_STRING_LENG TH, "%f", dbl);
return string (chs);
}

------------------------------------------------------------------

I find that each time when the double value converts to the char
array. The first 4 char will be set to 0, but from the 5th one will
be the right value. So in the end the string will be treated as a null
string. I use std::string.

Does anybody know why? I really appreciate for your help.

I don't know the answer, but as others have suggested, use a
stringstream.

Here's what I use:

template < typename T, typename U >
T lexical_cast( const U& u ) {
std::stringstre am ss;
T t;
if ( !( ss << u && ss >t ) ) throw std::bad_cast() ;
return t;
}
void foo( double dbl ) {
string str = lexical_cast<st ring>( dbl );
// now use str.
}

[cutecutemouse]

Thank you for all the replies. I've just tried two ways. To use
stringstream, like the template what Jim said, and another way with
sprintf_s. But the problem is the same. The first 4 character are
always set to some strange chars. I'm really confused with it...

[Daniel T.]

cutecutemouse <pl******@hotma il.comwrote:

Thank you for all the replies. I've just tried two ways. To use
stringstream, like the template what Jim said, and another way with
sprintf_s. But the problem is the same. The first 4 character are
always set to some strange chars. I'm really confused with it...

Show us the stringstream code that exhibits the problem you are having.

[Sam]

cutecutemouse writes:

Thank you for all the replies. I've just tried two ways. To use
stringstream, like the template what Jim said, and another way with
sprintf_s. But the problem is the same. The first 4 character are
always set to some strange chars. I'm really confused with it...

Go ask Microsoft. You were told, repeatedly, that this is not a standard C++
function, but some Microsoft-specific rogue mutation. Only Microsoft can
tell you what it does or how it works.

This newsgroup is not for discussions of Microsoft-specific language
variations, but rather the standard C++ language.

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[Victor Bazarov]

"Sam" <sa*@email-scan.comwrote in message
news:co******** *************** *******@commodo re.email-scan.com...
[???]

Sam,

It's not the first time I saw a posting from you that does not
seem to have any content. It turns out you use some kind of
format that causes your reply to appear as an attachment (which
in a text-only newsgroup is prohibited, and many actually have
those disabled). Could you perhaps set your newsreader so that
no attachment is made out of your reply and instead plain text
is used, please? It would make the lives of many of us easier.
That is, if you care whether anybody actually reads what you
post...

Thanks!

V
--
Please remove capital 'A's when replying by e-mail
I do not respond to top-posted replies, please don't ask

[Sam]

Victor Bazarov writes:

Sam,

It's not the first time I saw a posting from you that does not
seem to have any content. It turns out you use some kind of
format that causes your reply to appear as an attachment (which

Only in broken newsreaders.

in a text-only newsgroup is prohibited, and many actually have
those disabled). Could you perhaps set your newsreader so that
no attachment is made out of your reply

All my messages are always posted in plain text, and not an attachment:

Content-Type: text/plain; format=flowed; charset="US-ASCII"
Content-Disposition: inline
Content-Transfer-Encoding: 7bit

and instead plain text
is used, please?

Please stop blaming me for known ten-year old bugs in Microsoft's crapware.
Microsoft's crapware can't wrap its brain around digitally-signed messages,
that all modern newsreaders, such as Mozilla Thunderbird, have no problems
displaying, so it pukes and shows it as an attachment.

It would make the lives of many of us easier.
That is, if you care whether anybody actually reads what you
post...

Go tell Microsoft to fix their broken newsreader, and implement RFC 2015,
the standard for digitally-signed messages that's been published in 1996.

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