[fpc-pascal] if-then-else expression

[Serguei TARASSOV]

On 04/02/2016 12:00, fpc-pascal-request at lists.freepascal.org wrote:
> Date: Wed, 3 Feb 2016 14:34:34 +0100
> From: Sven Barth<pascaldragon at googlemail.com>
>
> Am 03.02.2016 12:11 schrieb "Serguei TARASSOV"<serge at arbinada.com>:
> >Holy sh*t, ?a continue !:)
> >Even if evaluation order will be assured and well documented, it doesn't make sense!
>> >Example :
>> >
>> >x := iif(Obj = nil, 0, Obj.Value); // Seems OK when right-to-left and stop on 'true' evalation
>> >x := iif(Obj <> nil, Obj.Value, 0); // Raise access violation
> The current IfThen() intrinsic is not a function call. Internally it gets
> replaced by an if-node thus from the compiler's point of view it behaves
> like an if-statement that assigns the expressions in its branches to a
> temporary variable (yes that one is thrown away during code generation...),
> thus the term evaluation order in the sense of calling functions does not
> apply at all anyway.
>
I see, and it is what I said many times: you wrap the if-statement into 
pseudo-function.
This make no sense and will be source of programmer's errors.
The simplest case is to add "uses Math" or "uses StrUtils" to hide 
intrinsic pseudo-function and crash the application.

iif bool-expression then expression-true else expression-false;
or
inline if bool-expression then expression-true else expression-false;

is only solution in my opinion.

Regards,
Serguei