convert double to string (string.h string)

[markman]

Im having a bit of trouble with conversions to this string thing (from string.h). Is there an all knowing conversion table or something of the like?

string s;
double d;
d = 3.14
s = string(d);
cout << s << endl; 

there isnt a constructor with a double argument...

[ChuckB]

Hi,
I just got this really cool summary of converting numbers to strings and vice versa from a German forum http://www.c-plusplus.de...submitted by the C++ moderator. Look beyond the German and you can read the code.

a) Zahl nach String: (numbers to string)

1. std::ostringstream


#include <sstream>
#include <string>
#include <iostream>
using namespace std;
int main()
{
    double d = 3.14;
    ostringstream Str;
    Str << d;
    string ZahlAlsString(Str.str());
    cout << ZahlAlsString << endl;
}

2. std::ostrstream

#include <strstream>
#include <string>
#include <iostream>
using namespace std;
int main()
{
    double d = 3.14;
    char buffer[10];
    ostrstream Str(buffer, 10);
    Str << d << ends;
    string ZahlAlsString(Str.str());
    cout << ZahlAlsString << endl;
}

3. sprintf

#include <stdio.h>
#include <stdlib.h>
int main()
{
    double d = 3.14;
    char buffer[10];
    sprintf(buffer, "%g", d);
    printf("%s\n", buffer);
    system("pause");
}


b) String nach Zahl (string to number)

1. std::stringstream

#include <sstream>
#include <string>
#include <iostream>
using namespace std;

int main()
{   
    string AlsString("3.14");
    stringstream Str;
    Str << AlsString;
    double d;
    Str >> d;
    cout << d << endl;
}
2. std::strstream


#include <strstream>
#include <string>
#include <iostream>
using namespace std;
int main()
{   
    string AlsString("3.14");
    char buffer[10];
    strstream Str(buffer, 10);
    Str << AlsString << ends;
    double d;
    Str >> d;
    cout << d << endl;
}
3. atof, atoi, atol


#include <cstdlib>
#include <iostream>
using namespace std;
int main()
{   
    const char* AlsString = "3.14";
    double d = atof(AlsString);
    cout << d << endl;
}
4. sscanf


#include <cstdio>
#include <iostream>
using namespace std;
int main()
{   
    const char* AlsString = "3.14";
    float d = 0;
    // ACHTUNG! sscanf erwartet ein float. Kein double!
    sscanf(AlsString, "%g", &d);
    cout << d << endl;
}
5. strtod, strtol, strtoul


#include <cstdlib>
#include <iostream>
#include <string>
using namespace std;
int main()
{   
    string AlsString("3.145");
    char* StopPosition = 0;
    double d = strtod(AlsString.c_str(), &StopPosition);
    cout << d << endl;
}

Regards,
ChuckB

[Zaei]

string streams are pretty nice =)...

strstream sstream;
sstream << "10" << endl;
sstream << 20 << endl;
string s;
long l;
sstream >> l
sstream >> s
cout << sstream.str() << endl << endl;
cout << l << endl;
cout << s << endl;

Z.

[parksie]

Zaei - use stringstreams, not strstreams

Oh, quick function for you:

template <typename T>
string toString(const T &ref) {
    ostringstream oss;
    oss << ref;
    return oss.str();
}

...or something

[Zaei]

Forgive me =). It was late =).

Z.

[markman]

Perfect everyone

Templates work in g++? Ill assume yes; otherwise reply

[parksie]

Well, if you use the 3-series, then yes.

3.2 is the latest I think...but it can't compile the kernel. Oops. Need 2.95.3 for that

[markman]

then *** is it a new version if it cant do that?

[CornedBee]

There may be some dropped extensions that the kernel used, this would explain why it doesn't work anymore.

Another explanation would be that it's simply a bug.

[parksie]

Most people point at the second. Linus recommends 2.95.3, and I haven't been able to compile the 2.5.38 kernel with anything else!

For most normal code, I use 3.2, because it's C++ support is far better.

2.95 can do templates, but it doesn't support the more esoteric features.

[CornedBee]

Why do you need the kernel recompiled?

[parksie]

The 2.5 series is the current development version.

/me is just playing

I built 2.4.19 on my other disk as part of a test (trying to put something minimalist together).

[Zaei]

Out of curiosity, is there any Linux IDE/Code Editor running around out there that has vim style code indentation?

Example:

int main()
{
>>>>code goes over here when I hit enter
>>>>same thing
} <<<< curley brace comes back over here, without me hitting that backspace key

vim, and MSVC are the only editors that I have seen that do this...

Z.

[parksie]

nedit and emacs can do it.

[Zaei]

Figured emacs could do it =).

Z.

[parksie]

It does everything.

If you've got it, at the console type

$ emacs -batch -l dunnet

Enjoy!

(found that one at work...my productivity dropped for a couple of weeks )

[markman]

Ok Im having a bit of trouble using the template. I cant make a prototype that works. They all stem massive ammounts of errors.

[parksie]

Code, and errors?

[CornedBee]

Edit++ in Windows can do it too...
But you probably won't get it running, not even under WINE, as it uses MFC and all kinds of weird windows features such as OLE drag/drop, embedded IE etc.

[CornedBee]

And while we're at gcc...

Anyone know where I can get a x86 binary of gcc 3.x or any C compiler that can compile gcc 3.2 for RedHat? I have a RedHat-derived server distro called e-smith (now SME server), and it doesn't come with any C compiler. Only as and ld (so if you got assembler source for any compiler it's ok too ).

[parksie]

Can't you just install the 2.95.3 binary RPM? That'll let you build 3.2.

[CornedBee]

Hmm, gotta search again, last time I looked I was sure I didn't find any RPM for gcc.

I'll look for it tomorrow.

[parksie]

There must be one, it needs to come with RedHat

[CornedBee]

Yet that doesn't mean it's available in public.

[parksie]

I don't follow. It must be available, almost by definition.

[Zaei]

Originally posted by parksie
It does everything.

If you've got it, at the console type

$ emacs -batch -l dunnet

Enjoy!

(found that one at work...my productivity dropped for a couple of weeks )

ROFL =). Thats pretty good =). Now, where is the emacs fridge? =).

Z.

[parksie]

It's quite a good game if you recognise the jokes, and if you've been hacking a while

I missed a fair few, but got enough to redeem myself

There's everything in there I'm busy trying to learn how to use it. Managed to create two files, get them in separate windows (Emacs windows, not X windows -- all terminal! w00t!) and compile, viewing the output

And all this running off cryptic keyboard shortcuts and no mouse...

[Zaei]

I feel a whole lot more comfortable in vim, but emacs seems a LOT more powerful... If im doing some coding, ill open two telnet sessions... leave one in vim, and use the other for compiling.. saves a lot of back and forth.

And who could think of NOT doing it without the mouse... I mean... what is that? =).

Z.

[parksie]

A lot more powerful? It has everything bar the kitchen sink. No, wait, that's in there

It even has keyboard shortcuts for moving around so you don't have to move from the touch-typing position to the arrow keys Quality stuff

[Zaei]

Its like an operating system... =).

Z.

[parksie]

Pretty much, yeah, only it has more features You can do most of what you'd often do from inside it, mail, news, programming.

Mostly everything except browse the web (although who knows, maybe...)

[Zaei]

lynx.. im sure you can use lynx from it... =).

Z.

[parksie]

/me tries if he can remember those damn key combos

[markman]

Originally posted by parksie
Zaei - use stringstreams, not strstreams

Oh, quick function for you:

template <typename T>
string toString(const T &ref) {
    ostringstream oss;
    oss << ref;
    return oss.str();
}

...or something

that.

[parksie]

You what?

[CornedBee]

emacs is a religion.

http://www.gnu.org/fun/humor.html

[markman]

This is the code that doesnt work without a prototype. What prototype should be used for this?

template <typename T>
string toString(const T &ref) {
    ostringstream oss;
    oss << ref;
    return oss.str();
} 

[CornedBee]

template <typename T>
std::string toString(const T& ref);


BTW I would inline this one.

[markman]

#include <iostream>
#include <string>
using namespace std;

template <typename T>
std::string toString(T &ref);

int main()
 {
    double d = 3.14;
    string s;
    s = toString(d);
    cout << s << endl;

}

template <typename T>
std::string toString(T &ref)
 {
    ostringstream oss;
    oss << ref
    return oss.str();
 } 

g++ -Wall test.cpp yields:
test.cpp: In function `int main ()':
test.cpp:10: universal-character-name `\u00a0' not valid in identifier
test.cpp:10: universal-character-name `\u00a0' not valid in identifier
test.cpp:10: sorry, not implemented: universal characters in
identifiers
test.cpp:10: universal-character-name `\u00a0' not valid in identifier
test.cpp:10: sorry, not implemented: universal characters in
identifiers
test.cpp:10: universal-character-name `\u00a0' not valid in identifier
test.cpp:10: sorry, not implemented: universal characters in
identifiers
test.cpp:10: `___double' undeclared (first use this function)
test.cpp:10: (Each undeclared identifier is reported only once for each
function it appears in.)
test.cpp:10: parse error before `='
test.cpp:12: `d' undeclared (first use this function)
test.cpp: In function `string toString (T &)':
test.cpp:20: universal-character-name `\u00a0' not valid in identifier
test.cpp:20: universal-character-name `\u00a0' not valid in identifier
test.cpp:20: sorry, not implemented: universal characters in
identifiers
test.cpp:20: universal-character-name `\u00a0' not valid in identifier
test.cpp:20: sorry, not implemented: universal characters in
identifiers
test.cpp:20: universal-character-name `\u00a0' not valid in identifier
test.cpp:20: sorry, not implemented: universal characters in
identifiers
test.cpp:20: parse error before `;'
test.cpp:22: parse error before `return'

[parksie]

I think something messed up when you typed it in. It's complaining at the tokenising level that you've got some bad characters in there.