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istringstream question

P: n/a
Hi,
Is there any way to initiate a istringstream object's string without
using constructor. I have tried the str() function but it did not work.
For example, I want to write the following code:

istreamstring iss(my_string);

then do somethings that involes the >> operator

then I want to change the string content in this buffer to other string
and use the >> operator on it again.

I have tried iss.str(my_new_string), but it does not work.Anybody knows
how to do this?

Thanks very much
Viet

Jul 19 '05 #1
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3 Replies


P: n/a
"Viet Le Hong" <lh****@iprimus.com.au> wrote
Hi,
Is there any way to initiate a istringstream object's string without
using constructor. I have tried the str() function but it did not work.
For example, I want to write the following code:

istreamstring iss(my_string);

then do somethings that involes the >> operator

then I want to change the string content in this buffer to other string
and use the >> operator on it again.

I have tried iss.str(my_new_string), but it does not work.Anybody knows
how to do this?


That is how you do it. It works for me. Post a complete, compilable code
sample and tell us where the error occurs.
Jul 19 '05 #2

P: n/a
That was the code I have written in my program, sorry I could not post
all my program because it's quite long. The next light function read new
line from a file, I have check the function and it works fine. The
problen happens after the >> call in the read eye part, it does not
change the value of "command" variable at all.
Thanks
Viet
camera res;
string command;
// read image size
next_line();
istringstream ss(buffer);
ss >> command;
if (command!="IMAGESIZE")
throw parser_error_exception("Invalid image size command when reading
camera");
else
{
int width, height;
ss >> width >> height;
res.set_image_size(width,height);
}

// read eye
next_line();
ss.str(buffer);
ss >> command;
if (command!="EYE")
throw parser_error_exception("Invalid eye command when reading camera");
else
{
double x,y,z;
ss >> x >> y >> z;
res.set_eye(x,y,z);
}

Jul 19 '05 #3

P: n/a
Viet Le Hong wrote:
That was the code I have written in my program, sorry I could not post
all my program because it's quite long. The next light function read new
line from a file, I have check the function and it works fine. The
problen happens after the >> call in the read eye part, it does not
change the value of "command" variable at all.
Thanks
What might have happened, is that the stream object is put into an
invalid state by one of the read operations. You should generally
test the state of a stream after every read. The clear () member
function is used to reset the state.

The comp.lang.c++ FAQ (Google for C++ FAQ) has a good section on IO
which is almost certain to help you get your code working.

Regards,
Buster.
Viet
camera res;
string command;
// read image size
next_line();
istringstream ss(buffer);
ss >> command;
if (command!="IMAGESIZE")
throw parser_error_exception("Invalid image size command when
reading camera");
else
{
int width, height;
ss >> width >> height;
res.set_image_size(width,height);
}

// read eye
next_line();
ss.str(buffer);
ss >> command;
if (command!="EYE")
throw parser_error_exception("Invalid eye command when reading
camera");
else
{
double x,y,z;
ss >> x >> y >> z;
res.set_eye(x,y,z);
}


Jul 19 '05 #4

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