[fpc-devel] Incomplete docs on operator precedence / Question about actual precedence
Michael Van Canneyt
michael at freepascal.org
Mon Feb 3 13:22:09 CET 2014
On Mon, 3 Feb 2014, Tomas Hajny wrote:
> On Mon, February 3, 2014 12:10, Sven Barth wrote:
>> Am 03.02.2014 12:04, schrieb Michael Van Canneyt:
>>> On Mon, 3 Feb 2014, Sven Barth wrote:
>>>> Am 03.02.2014 08:58, schrieb Michael Van Canneyt:
>>>>> As for unary minus: this is the same as a binary minus in arithmatic
>>>> Not quite. Take this example:
>>>> === output end ===
>>>> So unary minus (and also unary plus which is a valid operator as
>>>> well!) binds stronger than multiplication.
>>> Then that is an anomaly introduced by operator overloading.
>>> In math, -2^2 = -4
>> Yes and the same is true in FPC with operator overloading. If you add a
>> ** operator overload (which uses Trunc(Power(aLeft.i, aRight.i)) ) and
>> have this expression: -t1 ** t2 with t1.i = 2 and t2.i = 2 the result
>> will be -4 as well.
>> Please keep in mind that -2^2 is (-2) * (-2).
> ? -2^2 = -(2^2) = -4 <> (-2)*(-2) ?
> Also in FPC:
> WriteLn (-2**2);
> ...gives "-4".
I was already wondering whether all my education had gone for naught :D
More information about the fpc-devel