C++ Help.... how can i Round X to n digits?

[chiwawa626]

C++ Help.... Round X to n digits (after the decimal point)
so like
x= 1234.12345
n=2
answer would be 1234.12

how can i do that?!??!?!

 

[Platypus]

You want to set your IOS flags.

cout<<setiosflags(ios::left) | setprecision(2)<<blah blah<<;

Something like that, I haven't used that in a while, so the syntax may be a bit off.
Make sure "X" is a double.

 

[flood]

can anyone see why this wouldnt work?
((double)((long)(x*(10^n))))/(10^n)

 

[arcain]

how about:

variable = (double)((long)(variable + 0.5));

durr.. missed the 2 decimals part..

or in this case..

multiply variable by 100 and then divide by 100 afterwards..

 

[BigFatCow]

<< can anyone see why this wouldnt work?
((double)((long)(x*(10^n))))/(10^n) >>



you cant do 10^n, it would have to be pow(10,n)

make sure to include math.h

((double)((long)(x*(pow(10,x)))))/(pow(10,x));

that should work

 

[chiwawa626]

cout << setprecision(3);
cout.setf(ios::fixed, ios::floatfield);
cout<<x;


WORKS!

 

[Platypus]

yes, i forgot the ::fixed and the floatpoint.
It's been a few years since I needed that.

I am glad it worked for ya

Edit: make sure to #include the iomanip.h library...

 

[flood]

<<

<< can anyone see why this wouldnt work?
((double)((long)(x*(10^n))))/(10^n) >>



you cant do 10^n, it would have to be pow(10,n)

make sure to include math.h

((double)((long)(x*(pow(10,x)))))/(pow(10,x));

that should work >>



well, of course
((double)((long)(x*(pow(10,x)))))/(pow(10,x));
doesnt work properly all the tine tho

 

[hans007]

the setios stuff would just make it print differently. the value would still be the same. to round it you'd probably wanna go do this..



say n is 2.


then multiply it by 10^2.


use a truncation function, or cast it , x=(long) (number * pow(10,n)) to truncate the decimals;

then take the number, cast it back into a double and divide by number= (double) /pow (10,n)