Define a string

[aeo3]

I need to put a filename is mixed from characters and numbers but these numbers are variable, for example;
char filename[]="xxx" then var "xxx" then var;
i.e., filename="ind23 ept12 " where 23 is var x and 12 is var y.


int x;
int y;
char filename[20];
cin>>x>>y;
char *filename;
filename=strcpy (filename,"inf_ h_");
filename=itoa(f ilename,x);
filename=strcpy (filename,"_f_" );
filename=itoa(f ilename,y);
myfile.open("fi lename");

[Matthew Page]

I don't know if it plays well in the C++ world, but for C you can use the sprintf function. The format would be the same as the printf function except that the first argument is the string you want to write to.

[RRick]

Sprintf should work in C++. Just include the c header file.

The C++ solution is to use something called an ostringstream. They are found in the <sstream> header file. You use them like cout and then extract the string info with str(). For example:

ostringstream oss;
oss << "path" << 11 << "/file" << 22.22;
cout << oss.str()

will print out "path11/file22.22"

[aeo3]

When I am trying to use ostringstream oss;
undecalare ostringstream

[Meetee]

When I am trying to use ostringstream oss;
undecalare ostringstream

For that you need to add headers

#include <iostream>
#include <sstream>

Try std::ostringstr eam instead of ostringstream.

Regards

[aeo3]

Thanks it works, but i need to put this string in another variable, for instance
char filename[25];
filename=oss.st r();
but the error message appears which is incompatible types in assigment of 'st::basic_stri ng<char,.....

[Meetee]

but the error message appears which is incompatible types in assigment of 'st::basic_stri ng<char,.....

Read above lines again. You might have written st:: instead of std::

That may be the cause of error. Please check it.

Regards

[aeo3]

char filename[25];
std::ostringstr eam oss;
oss<<"inf_h_"<< x<<"_f_"<<y<<". txt";
filename=oss.st r();
this is a part of my code,
the error message is : incompatible types in assigment of 'std::basic_str ing(char,std::c har_traits<char >, std::allocator< char>>' to char[25]
also, i tried to use pointer to char, but error messages appears.

[Darryl]

[CODE=cpp]char filename[25]
filename=oss.st r();
[/CODE]

you can't assign char arrays this way, only in construction like

char filename[25] = oss.str().c_str (); //plus you needed c_str()

but since you are using stringstreams anyway, easier would be

oss >> filename;

[RRick]

aeo3,

Watch how you mix these structures together. You're mixing C with C++. You can do it, but you need to be careful. One solution is to stay with C++ and use strings, and the various streams like cout and ostringstream.

If you want to use char * or char buffer[23], then you're mixing C and C++ together. You can it, but its not for the novice. For example:

const char * buffPtr = oss.str().c_str();

will work, but you can't modify the buffPtr values.

If you want to put the values in char buffer[23], then you will have to use the C string copy routines. For example:

char buffer[23];
strncpy( buffer, 23, oss.str().c_str());

but now buffer might not be terminated with a '\0' and you'll probably have to cast the oss c_str to (char *).

When I deal with strings, I keep them in the C++ string class and only use c_str(), when I have to pass them off to some routine.

[sicarie]

aeo3-

Check your PM's in the top right of the page.

Thanks,

sicarie

[aeo3]

I think it is good idea, thanks a lot.
The only way that I found to use ostringstream is by adding std::ostringstr eam also, when I'm trying to define a string variable;
string var;
it is not accepted as a variable type
So, array of char is the alternative way to deal with it. But what is c.str()?.
The idea that i need to do, my program will generate a series of output files, and i need to distinguh between these files according to the value of two integer variables.

[sicarie]

aeo3-

This is your last chance to respond to my PMs.

[aeo3]

to sicarie

what is the problem, you send me a message, i do not know the reasons to tell me something like that why? what happen?

[sicarie]

aeo3-

Go to the top right corner of the page - you will see a number followed by "PMs". Click on it, read them, and respond.