question about setprecision

[tnjones]

Hello,
I have this program where I have to do some calculations with data read from a text file with different number formats. For example the file may consists of:
9.09090901
18.1818178
27.2345891
8.9090090
100.99991
After doing such calculations the final result should be one decimal place. For Example, if I have 9.09090901 I want it to be printed as 9.1. However, I have this working with setprecision(2) but if the number in the file is 18.181878 it retrns 18, which is incorrect, I need it to return 18.2. With this is mind, is there any way all numbers are rounded one decimal place.By any chance is there anyone can tell me how to do this or give some advice.Any help will be greatly appreciated.

[helios]

http://www.cplusplus.com/reference/iostream/manipulators/setprecision.html
And then this:
http://www.cplusplus.com/reference/iostream/ios_base/fmtflags.html

[buffbill]

Couldn't you use some logic such as ?
If result - int(result) >=0.5 ceil else floor

[helios]

He doesn't want to truncate. He wants to round.

[buffbill]

my book says that ceil and floor rounds but ooops ....only to the nearest integer and must deal with a floating point number. i guess i need to read your references also!

[jsmith]

So another way to round to exactly one decimal place is first to multiply the answer by 10, then round to nearest integer, then divide by 10. I'm not going to speak of the accuracy of the result due to floating point roundoff error though.

[Syx]

You can easily do that by using the manipulators fixed (to output your floating point in a fixed decimal format) and showpoint (to force the output to show the decimal point and trailing zeros when the decimal numbers are zero).
Manupulator fixed used with a setprecision of 1 will force all your numbers to be displayed with one decimal place and with showpoint even your 5th number will round up to 101.0


Just do:
cout << fixed << showpoint << setprecision(1);
before outputting your numbers.

Good luck!