"in" everywhere

[Michel Fortin]

On 2010-10-07 11:47:21 -0400, Andrei Alexandrescu 
<SeeWebsiteForEmail at erdani.org> said:

> On 10/7/10 10:39 CDT, Daniel Gibson wrote:
>> Andrei Alexandrescu schrieb:
>>> On 10/7/10 9:59 CDT, Daniel Gibson wrote:
>>>> Andrei Alexandrescu schrieb:
>>>>> On 10/7/10 6:54 CDT, atommixz wrote:
>>>>>> It would be nice if it were possible to use the "in" expression
>>>>>> wherever
>>>>>> possible. Now it is only implemented for associative. arrays. (Weird).
>>>>>> Examples of how this could be used:
>>>>>> - Find string in string
>>>>>> - Search for a character in a string
>>>>>> - Search for an item in the array, array of characters, array of
>>>>>> strings,
>>>>>> tuples, enum, structure
>>>>>> - what else?
>>>>>> 
>>>>>> In Python done something like this.
>>>>>> 
>>>>>> Here it would be useful to me
>>>>>> http://code.google.com/p/atommixz/source/browse/analyze-x86/analyze-x86.py
>>>>>> 
>>>>>> 
>>>>>> http://code.google.com/p/atommixz/source/browse/analyze-x86/analyzex86.d
>>>>>> 
>>>>> 
>>>>> I'm a bit leary of adopting this feature (it has been discussed). To
>>>>> me "in" implies a fast operation and substring searching isn't quite
>>>>> it.
>>>>> 
>>>>> One thing that could be done is to allow "in" with literal arrays to
>>>>> their right:
>>>>> 
>>>>> if (x in ["abcde", "asd"]) { ... }
>>>>> 
>>>>> The size of the operand is constant, known, and visible.
>>>>> 
>>>>> 
>>>>> Andrei
>>>> 
>>>> That feels inconsistent.. to be able to use it with "literal arrays to
>>>> their right" (and what about fixed size arrays?) but not with actual
>>>> arrays and dynamic arrays seems weird.
>>> 
>>> It's not. It's all about constant size in the size of the input vs.
>>> arbitrary size. Makes perfect sense to me.
>>> 
>> 
>> So what about static arrays?
> 
> Same deal - same as literal arrays: they can be searched. The expected 
> run time is known during compilation and independent of the input size.

What about a static array of 200000 elements? At which point does it 
become linear?

I'm okay with it for compile-time constant literals, because the values 
are known at compile time and the compiler can optimize the search at 
compile time (so it doesn't have to be linear), but for static array 
where the content isn't known at compile time, I'd not allow it.

Perhaps it could be allowed with a tuple. :-)

	if (x in ("abcde", "asd")) { ... }

-- 
Michel Fortin
michel.fortin at michelf.com
http://michelf.com/