PRTDEC.THD  --- Copyright 1987 by Phil Wheeler

An original compilation of Compuserve Model 100 Forum messages for use by
Forum members only.

Printing decimal numbers with truncated precision is often needed by Basic
programmers.  These message discuss ways to use PRINT USING and INT for this
purpose.  Note that you can modify these approaches slightly to get rounding
-- but this is left as an exercise for the reader of the THD!

Message range: 157672 to 157698
Dates: 10/4/87 to 10/5/87


Sb: #decimal truncate
Fm: James Yi 73327,1653
To: All

I lost my Basic manual, so when these things come up, I have to ask.
Does anyone know if it is possible to truncate decimal places, so that only cer
tain amount of digits in the decimal places can be displayed?


Fm: Eiji Miura 76703,4311
To: James Yi 73327,1653

You can use PRINT USING statement.  The format is

  PRINT USING "format"; expression list

For example, to have two decimal places, "format" will be something like
"######.##"

10 A=3.14159265
20 PRINT USING "######.##"; A

This program will output 3.14.


Fm: Tony Anderson 76703,4062
To: James Yi 73327,1653

Yes.  You can truncate with the PRINT USING type of statement, where you
specify the format.  Since it covers 3 pages in the manual, it's sort of
difficult to summarize here... send me your address.

An alternate way is to force the number into a specific number of decimal
places, and then just display the number.  Here's an example which will force a
number to 2 decimal places:

10 X=17.123456789012345
20 Y=INT(X*100)/100
30 PRINT Y

To scale for three decimal places, change both 100's in line 20 to 1000, etc.


Fm: James Yi 73327,1653
To: Eiji Miura 76703,4311

Thanks Eiji, but I was looking for a Basic statment that would specify decimal places for just PRINT x.


Fm: James Yi 73327,1653
To: Tony Anderson 76703,4062

Well, it doesn't look like there is one, but I was hoping for a single Basic
statement that would truncate decimal places of all numbers following it,
which is very convenient when you have many different variables to print.

I guess the next best alternative is PRINTUSING, which I'm not familiar with.
3 pages!?.


Fm: Tony Anderson 76703,4062
To: James Yi 73327,1653

Yep, there are a lot of options to PRINT USING.

However, what's wrong with the formula I gave you?  You can reduce it to a
single statement if you want....

PRINTINT(X*100)/100

If you have a "bunch" of variables to print, just do the same thing to each
variable.

However, I believe what you're looking for may be doable with the PRINTUSING
statement, in the form,

PRINTUSING,"###.##";A,B,C

Or something like that. But it won't format the list of variables for you...
just print them, one right after the other. It's difficult to say, when all we
have to go on, is, "print a bunch of variables".


Fm: James Yi 73327,1653
To: Tony Anderson 76703,4062

The variables are components of vectors,and it would be nice if all
three numbers could neatly fit in a single line,making it more readable.
Since I want to attach "i","j", and "k" to each numbers, PRINT USING
"#",a,b,c might not work. After looking at it again, I'll go with
PRINTINT(x/1000)*1000.


Fm: Tony Anderson 76703,4062
To: James Yi 73327,1653

Careful about where you put the "/" and "*"... what you listed won't work. It
returns a zero.  Gotta be INT(X*1000)/1000, not (X/1000)*1000.