precision on scientific notation

[rompecabezas]

i wanna change the precision of a number in scientific notation. e.g.: i have 3.459560456e-3 and i want a precision p=3, that is 3.46e-3... if i multiply by pow(10,3), then round and divide,the answer would be 0.001...

is maybe ios_base::precision the solution?
i don't know how to use it ... how can i declare an object that kind? i want it to deal with variables, not a std output..

any hints welcome!

[kbw]

Are you talking about displaying the number to a certain number of significant digits or are you talking about storing the number rounded number?

[buffbill]

cout.precision(?) sets a floating point format to display (?) digits. The original precision is rounded as required. I suspect that cout.width(7) would be appropriate if needed.

[rompecabezas]

YEAH, buffbill, i want to do exactly that ".precision()", but i do not want to display it, i want to store it in a variable. so kbw, i am talking about storing ;)

i would like to declare some variable <roundNum> so i could round my number <num> up to <x> significative digits doing sthg like roundNum.precision(x)

???

[twiss]

http://www.cplusplus.com/forum/general/4011/

[twiss]

Did it help?