"in" everywhere

[Steven Schveighoffer]

On Thu, 07 Oct 2010 13:51:36 -0400, Daniel Gibson <metalcaedes at gmail.com>  
wrote:

> Steven Schveighoffer schrieb:
>> On Thu, 07 Oct 2010 10:09:17 -0400, Daniel Gibson  
>> <metalcaedes at gmail.com> wrote:
>>
>>> Steven Schveighoffer schrieb:
>>>> On Thu, 07 Oct 2010 07:54:14 -0400, atommixz <atommixz at gmail.com>  
>>>> 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?
>>>>  This has been suggested before.  The problem is that 'in' is  
>>>> generally considered to be a fast operation (< O(n)) so linear search  
>>>> is out.
>>>>  -Steve
>>>
>>> Is it?
>>> I wouldn't expect it to be < O(n) on a regular array, but it'd still  
>>> be convenient to have instead of iterating over the array and  
>>> comparing the contents yourself.
>>  The problem is with generic code.  Generic code that accepts some type  
>> that defines the "in" operator.  What can that generic code expect for  
>> performance when using "in"?  As a general rule, generic programming  
>> must always assume the worst case, and if we have no rules for 'in',  
>> the worst case is linear.  Which means generic code may not use 'in'  
>> when it would be a fast operation.  Same thing with indexing.  Try  
>> sorting a 'random access' range which uses a linear search on opIndex,  
>> and see what the performance is.
>>  In addition, arr.find(x) seems pretty simple to me.
>>  -Steve
>
> I didn't know about arr.find(). Is that documented somewhere?
>
> I do however agree that arr.find() is sufficient if it's there.

std.algorithm.find:  
http://www.digitalmars.com/d/2.0/phobos/std_algorithm.html#find

arr.find works because of the universal call syntax for arrays makes  
arr.find(x) equivalent to find(arr, x).

-Steve