Solved

truncate

Posted on 1998-10-18
9
1,163 Views
Last Modified: 2008-03-10
VC5

Is there function that i can truncate
a double of value 3.333333333333333......
to a fewer number of decimal point?

double D = 3.33333333..... // return by some function
double MyNewD = truncate_D_to_2_decimal_point(D) // ???



0
Comment
Question by:leowlf
9 Comments
 
LVL 3

Expert Comment

by:arnond
ID: 1175414
one way is to do:

double truncate (double D,int n)
{
  long multiplied;
  double to_return;

  multiplied = (D*pow(10,n));         // save only the first n digits after the decimal point . (as a long integer).
  to_return  = (multiplied / (pow(10,n));  // return to the trtunced (original ) number.
 
  return (to_return);
}
 
for example:
in truncate (0.123456789,5) you'll get:
multiplied = 12345
to_return = 0.12345
 
0
 
LVL 22

Expert Comment

by:nietod
ID: 1175415
That would work, but you have to understand that because of the limitations of the floating point format, not all decimal numbers will be expressible, thus when you truncate the number, you may see the last digit or two change in value.  This is not problem with arnond's method, this is a limitation of the floating point system.  For this reason, most programmer's don't truncate the value at all.  They may limit the number of digits that print, but will try to retain full precision internally.
0
 
LVL 3

Expert Comment

by:arnond
ID: 1175416
nietod is right, you can limit the number of digits you print using the format specifications of your favorite output function. for example: in printf() you should use "%.pf".
the 'p' stands for precision, i.e.: how many decimal places to display.

0
Comprehensive Backup Solutions for Microsoft

Acronis protects the complete Microsoft technology stack: Windows Server, Windows PC, laptop and Surface data; Microsoft business applications; Microsoft Hyper-V; Azure VMs; Microsoft Windows Server 2016; Microsoft Exchange 2016 and SQL Server 2016.

 
LVL 3

Expert Comment

by:arnond
ID: 1175417
leowlf,
did my suggestion help ?
would you like me to post an answer for this question ?
0
 

Author Comment

by:leowlf
ID: 1175418
arnond,
Your suggestion is good enough for me,
please post an answer.
Thank you.
0
 
LVL 3

Accepted Solution

by:
arnond earned 50 total points
ID: 1175419
Here's my dummy answer.
Thanks.
0
 
LVL 1

Expert Comment

by:pibarale
ID: 24084984
Hi Arnod,
I am using C language because I can not use C++ due to some desing issue.
how do we proceed if the double has this value
UINT s = 10;
int n = 16;
double dx = (double)(s/100.0);
here is dx = 0.10000000000000001
The above logic does not work.
0
 
LVL 84

Expert Comment

by:ozo
ID: 24085285
> you have to understand that because of the limitations of the floating point format, not all decimal numbers will be expressible, thus when you truncate the number, you may see the last digit or two change in value.
0
 
LVL 1

Expert Comment

by:pibarale
ID: 24104023
Thanks OZO. This is also my understanding.
One concern we are use C code in such a huge platform like Win32 (using VS 2008 compiler). Can this irreguarity be fix by the vendor in near future?
With this I stop with satisfaction.
0

Featured Post

Netscaler Common Configuration How To guides

If you use NetScaler you will want to see these guides. The NetScaler How To Guides show administrators how to get NetScaler up and configured by providing instructions for common scenarios and some not so common ones.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Errors will happen. It is a fact of life for the programmer. How and when errors are detected have a great impact on quality and cost of a product. It is better to detect errors at compile time, when possible and practical. Errors that make their wa…
Written by John Humphreys C++ Threading and the POSIX Library This article will cover the basic information that you need to know in order to make use of the POSIX threading library available for C and C++ on UNIX and most Linux systems.   [s…
The goal of the video will be to teach the user the concept of local variables and scope. An example of a locally defined variable will be given as well as an explanation of what scope is in C++. The local variable and concept of scope will be relat…
The viewer will learn how to pass data into a function in C++. This is one step further in using functions. Instead of only printing text onto the console, the function will be able to perform calculations with argumentents given by the user.

777 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question