[fpc-devel] *** GMX Spamverdacht *** Re: Dangerous optimization in CASE..OF

[Ozz Nixon]

following the grammar, I would suggest “in” when trying to do what you want, not “is”.

if a in 3..10 then begin

to me reads more accurately than

if a is 3..10 then begin

is the keyword is implies 1, just like the English language, whereas, in and are implies multiple or in this case range.

> On Apr 14, 2018, at 9:02 AM, Thorsten Engler <thorsten.engler at gmx.net> wrote:
> 
> For objects "is" compares (the type of) the value (not the type of the variable) against the specified type. Effectively telling you if you can do a hard cast of that value to that type.
> 
> For ordinals, it compares the value against the specified type. Effectively telling you if you can do a hard cast of that value to that type.
> 
> I fail to see the difference?
> 
>> -----Original Message-----
>> From: fpc-devel <fpc-devel-bounces at lists.freepascal.org> On Behalf
>> Of Ozz Nixon
>> Sent: Saturday, 14 April 2018 22:43
>> To: FPC developers' list <fpc-devel at lists.freepascal.org>
>> Subject: Re: [fpc-devel] *** GMX Spamverdacht *** Re: Dangerous
>> optimization in CASE..OF
>> 
>> I understand the thread, however, in one of the ISO standards for
>> Pascal, the keyword is, is defined for type not value. The example
>> I gave is the only way I can see supporting is on non objects -
>> because we are a typed language. That was my point, not arguing
>> against, however, sharing a way I could see a value of it. Other
>> than that, I am against...
>> 
>> Ozz
>> 
>>> On Apr 14, 2018, at 8:38 AM, Thorsten Engler
>> <thorsten.engler at gmx.net> wrote:
>>> 
>>> Eh, Ozz? Did you actually read this thread?
>>> 
>>> It has nothing to do with the declared type of i. it compares the
>> current value of i against the range of the specified type and will
>> return true if the current value falls inside that range.
>>> 
>>> 5 is TSubRange -> true
>>> 2000 is TSubRange -> false
>>> 
>>> Also:
>>> 
>>> case i as TSubRange of //exception if i < -5 or i > 5
>>> 
>>> 
>>> 
>>>> -----Original Message-----
>>>> From: fpc-devel <fpc-devel-bounces at lists.freepascal.org> On
>> Behalf Of
>>>> Ozz Nixon
>>>> Sent: Saturday, 14 April 2018 22:13
>>>> To: FPC developers' list <fpc-devel at lists.freepascal.org>
>>>> Subject: *** GMX Spamverdacht *** Re: [fpc-devel] Dangerous
>>>> optimization in CASE..OF
>>>> 
>>>> I have to ask why?
>>>> 
>>>> i is Int64 only, will always be int64 only, so all other
>> comparisons
>>>> are always skipped.
>>>> 
>>>> I could see this, inside a method with an untyped parameter:
>>>> 
>>>> procedure doSomething(myvar;out success:boolean); Begin
>>>>  {… your if is comparisons …}
>>>> end;
>>>> 
>>>> This opens your method to be used for all types for param1.
>>>> 
>>>> Ozz
>>>> 
>>>>> On Apr 14, 2018, at 5:51 AM, Thorsten Engler
>>>> <thorsten.engler at gmx.net> wrote:
>>>>> 
>>>>> I haven't checked out the changes you made to the compiler, so
>>>> you might have already covered this, but while you are at it,
>> you
>>>> might want to just make this work for any ordinal type with a
>> well-
>>>> defined upper/lower bound (any type for which High()/Low() can
>> be
>>>> evaluated at compile time). So:
>>>>> 
>>>>> type
>>>>> TSubRange=-5..5;
>>>>> TEnum=(One, Two);
>>>>> 
>>>>> var
>>>>> i: Int64;
>>>>> 
>>>>> begin
>>>>> if i is TSubRange then
>>>>>  //...
>>>>> If i is TEnum then
>>>>>  //...
>>>>> If i is SmallInt then
>>>>>  //...
>>>>> 
>>>>> (same with "as").
>>>>> 
>>>>> 
>>>>> 
>>>>>> -----Original Message-----
>>>>>> From: fpc-devel <fpc-devel-bounces at lists.freepascal.org> On
>>>> Behalf Of
>>>>>> Ondrej Pokorny
>>>>>> Sent: Saturday, 14 April 2018 19:03
>>>>>> To: fpc-devel at lists.freepascal.org
>>>>>> Subject: Re: [fpc-devel] Dangerous optimization in CASE..OF
>>>>>> 
>>>>>> On 14.04.2018 10:39, Thorsten Engler wrote:
>>>>>>> How about following the same schema as with classes?
>>>>>>> 
>>>>>>> If 1 is TMyEnum then
>>>>>>> //use hard cast here
>>>>>> 
>>>>>> Yes, that is reasonable as well and it will be easier to
>>>> implement
>>>>>> than the TryIntToEnum/IntToEnum intrinsics for me.
>>>>>> 
>>>>>> Ondrej
>>>>>> _______________________________________________
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>>>>> 
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>>> 
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