[fpc-devel]RangeChecking & NOT operator

[Paul Yanchenko]

Good day for you, Florian!

Wednesday, April 10, 2002, 4:18:44 PM, you wrote:

>>Runtime error 201 at line 5
>>But that's not the behavior I would have expected.
>>I think this is a bug.

FK> Hmmm, not really. FPC does all evalutation of ordinal expressions with the
FK> natural integer size of the CPU thus everything is evaluted as 32 Bit =>
FK> NOT b eavlutes to $ffffffff which doesn't fit into a byte.

FK> This behavior is different to good old TP but it is conform with ANSI-Pascal
FK> standard. I did this decision 9 years ago when a started FPC, maybe it was 
FK> wrong but in a lot of cases it makes the expression evalution more logical.

I don't think so. I think the result of operator should have same type
as an argument of operator. If we need different type - we shall use
type modifier ( not longint(b) ). Maybe exception is the case when
specified const value, i.e. for example (not 0) - there result type is
undefined.

BTW, what if we using type bigger than integer size of the CPU? I
tested this and

var
  qw:qword;
begin
  qw:=0;
  writeln(not qw);
end.

In 1.0.4 program just written me character "/". Why it so - I don't
know. But 1.0.5 report me result that more similar to true:
18446744073709551615.

Anyway, in the snapshot (at least 1.0.5 [2001/12/16] for i386) it
seemes to work exactly as I offer. Just don't change anything! ;-)


-- Someone who loves to program and enjoys being clever about it