[fpc-pascal] Why this evaluates on "if" wrong ?

Daniël Mantione daniel.mantione at freepascal.org
Sun Oct 28 19:08:09 CET 2007

Op Sun, 28 Oct 2007, schreef Milan Marusinec:

> Hello folks,
> This one looks pretty elementary, but to my big surprise
> it doesn't work as I would expect.
> I'd like to ask FreePascal compiler creators, how can I safely
> evaluate double variables in case like this.
> Sample program with comment is in attachement ...

If you do on a hand calculator:


... you will see:


If you multiply again with 3, you will see:


... and not 1.00000000000.

There is a similar issue here. The value "0.4" cannot be stored exactly in 
a computer, therefore it is rounded.

This behaviour normal and while annoying, it is simply how things work 
in the digital world, you will have to work around it.


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