Float to String

[EzarKun]

Hi,
I am a C++ newb, can anyone write up a piece of code that converts a float variable into a string.
Say I had a float var:


float var1 = 34.3212;

I want to convert it to a string, and the string when put to the terminal should look like this


String of Float = 34.32

that is I was a precision of 2.

Thanks everybody.

[Wybiral]

http://cppreference.com/stdio/sprintf.html

You can set the precision with the standard printf formating (it's on that site too).

EDIT:

Ooops... Sorry, I thought you were using C. In that case: http://cppreference.com/cppsstream/index.html

[aks44]

To convert a float to a std::string, use std::stringstream (http://www.cplusplus.com/reference/iostream/stringstream/).

To directly output a float to the console, use std::cout (http://www.cplusplus.com/reference/iostream/cout.html).

Both have the necessary methods to control the formatting (including the precision).

Specifically, see std::ios_base::precision() (http://www.cplusplus.com/reference/iostream/ios_base/precision.html) and std::ostream::operator<<() (http://www.cplusplus.com/reference/iostream/ostream/operator%3C%3C.html).

[EzarKun]

thanks for the quick replies, see what I can do.

[EzarKun]

sorry for the bother again, but I am stuck with the precision bit.
When I say
setprecision(2) for a value like 32.341212
the result is 32
I was 32.34, that is the 2 numbers after the decimal, for the use of currency.
thanks.

[adelgado]

Try setting the precision at 4 :-)

Greetings

[aks44]

From std::ios_base::precision() (http://www.cplusplus.com/reference/iostream/ios_base/precision.html) documentation (relevant parts in bold, follow the links in the documentation for more details):

The floating-point precision determines the maximum number of digits to be written on insertion operations to express floating-point values. How this is interpreted depends on whether the floatfield format flag is set to a specific notation (either fixed or scientific) or it is unset (using the default notation, which is neither fixed nor scientific):

* On the default floating-point notation, the precision field specifies the maximum number of meaningful digits to display in total counting both those before and those after the decimal point. Notice that it is not a minimum and therefore it does not pad the displayed number with trailing zeros if the number can be displayed with less digits than the precision.
* In both the fixed and scientific notations, the precision field specifies exactly how many digits to display after the decimal point, even if this includes trailing decimal zeros. The number of digits before the decimal point does not matter in this case.




Try setting the precision at 4 :-)
And have 1234.56 be output as 1234? :-p

[EzarKun]

From std::ios_base::precision() (http://www.cplusplus.com/reference/iostream/ios_base/precision.html) documentation (relevant parts in bold, follow the links in the documentation for more details):





And have 1234.56 be output as 1234? :-p

hey thanks, it works

[iharrold]

#include <iostream>
#include <sstream>

int main (void)
{
float val1 = 0.1091;

std::ostringstream buffer;
buffer <<std::fixed<<std::precision(2)<<val1;
std::string some_string = buffer.str();

std::cout<<some_string<<std::endl;
return 0;
}



Hrm... too slow.. very too slow.

[aks44]

Hrm... too slow.. very too slow.

Slow? Compared to what? Have you done measures? :-\"

[iharrold]

Slow? Compared to what? Have you done measures? :-\"

Heh.. meant my reply, not the code.

[aks44]

Heh.. meant my reply, not the code.

LOL sorry for the confusion. :)