----boundary-LibPST-iamunique-445470869_-_-
Content-type: text/plain
> > The REAL variable is not rounded in any way, but rather the int
> > (or long) is converted to a REAL, in this example without loss of
> > precision (as the integer 1 can be represented exactly as REAL).
> > The comparison is then performed between two real numbers,
> > and I would expect that the tests both either return true or false.
>
> I think that these two answers neatly illustrate the confusion.
> Dominik, who is definitely a better expert than I am, expects
> both cases to be consistent.
oops, you misunderstood me. I was referring to the two cases
tst := (r = long);
and
tst := (r = int);
which both should return the same result.
I am very cautious with *any* expectations regarding floating point
expressions. Another example? Here is one:
VAR x, y: REAL;
x := 9007199254740993;
y := 9007199254740994;
StdLog.Real(y - x);
> I repeat my question. Is this confusion warranted, or should rather
> the implementation of the compiler be tightened up such that an
> explicit type cast would be required for the relations. In other words,
> the relation (realVar = intVar) would not compile? Is this a sensible
> solution, or should it rather be left open for implementers?
so, after you solved the above example, you will also argue, that
the assignment of integers to real variables should also be prohibited,
and we are back to Modula-2.
But in your example the problem is not the comparison between
two reals, because this comparison is performed exactly, without
any rounding problems! The point is, that 1.000000000000000001
cannot be represented exactly in 64bits (similarly to the real number
0.1, which also cannot represented exactly in 64 bits).
Probably the easiest would be, to drop floats all together......
- Dominik
--------------------------------------------
To unsubscribe from this mailing list, send a message containing the word "unsubscribe" to:
blackbox-request{([at]})nowhere.xy
To get a list of valid e-mail commands and instructions on their usage, send a message containing the word "help" to the above address.
Send any problem reports or questions related to this email list to the list owner at
owner-blackbox{([at]})nowhere.xy
Current posting policy:
a) To post you should use the same address by which you are subscribed to the mailing list. That way, the list server will recognize you as subscriber and forward your posting immediately, without creating any overhead.
b) If, for some reason, you cannot post from the address, by which you are subscribed, your message will be moderated to avoid spam. Please understand that moderation will often cause some delay, in particular over weekends or holydays.
----boundary-LibPST-iamunique-445470869_-_-
Content-type: application/rtf
Content-transfer-encoding: base64
Content-Disposition: attachment; filename="rtf-body.rtf"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----boundary-LibPST-iamunique-445470869_-_---
Received on Mon Feb 17 2003 - 22:56:24 UTC