boost string format question

[wanting2learn]

I I need to format a string so that it is only a certain amount of characters long.

I have a function that returns an float which can be any number at all.
e.g.
1.123456
23.12345
0.123
123.123

I am using boost and I am doing this:

void myFunction( float myFloat)
{
   std::string tmp = boost::str(boost::format("%1%")%myFloat);
}

The above will result in no formatting at all.
How do I format my number so that it is only ever 3 characters before the decimal point and 2 after the decimal point. i.e my string will only ever be 6 characters long (including the decimal point)

many thanks

[jsmith]

boost::format( "%3.2f%" )

or

boost::format( "%|3.2f|" )

however keep in mind that if the number actually has 4 digits to the left of the decimal point, you'll get all 4, which
will blow your 6-character limit. You'll need to postprocess that (and deal with a floating point number that has
7 digits to the left of the decimal).

[wanting2learn]

thanks jsmith that now works.

But, why, if the number has got 4 digits will the 4 digits be included in the format, should it not truncate it??

thanks

[jsmith]

Of what use would boost::format be if it truncated? Would you want it to truncate 1234567 to 123456 or 234567,
neither of which is even close to the number you asked it to output?