[Oberon] real math

[Jörg]

Hi Zdenek

I just compiled your code with AOS on Windows.

- - - - 
MODULE RealTest;
IMPORT Commands;

PROCEDURE Do*(ctx: Commands.Context);
  VAR
    r: REAL;
  BEGIN
    r := 480 / 100 * 100;
    ctx.out.Int( ENTIER(r*1000000), 0);
  END Do;

BEGIN
END RealTest.Do ~
- - - - - 

On my PC the output is 480000000. So, I don't have the same effect as you
have.

Generally, checking REALs on equality is a little dangerous. You should
rather subtract two REALs and check for an epsilon>0.

I wonder what the use case of your code is? What do you want to find out by
dividing 480 by 100 and multiplying it by 100 again. Do you want to round a
number to two digits?

br
Jörg

-----Original Message-----
From: oberon at moravcik.info [mailto:oberon at moravcik.info] 
Sent: Sonntag, 9. November 2014 20:36
To: oberon at lists.inf.ethz.ch
Subject: [Oberon] real math

Hi,

following code returns imprecise real number:

 r : REAL;

 r := 480 / 100 * 100;
 out.Int( ENTIER(r * 1000000) , 0 );

outputs 48000019 instead of 48000000

How to check that 480/100*100 is 480 again ?

Thanks
Zdenek

--
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https://lists.inf.ethz.ch/mailman/listinfo/oberon
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