typeof(SortedRange) and is operator

[RazvanN via Digitalmars-d-learn]

On Tuesday, 8 November 2016 at 13:59:19 UTC, Nicholas Wilson 
wrote:
> On Tuesday, 8 November 2016 at 13:22:35 UTC, RazvanN wrote:
>> Sorry, I accidentally posted the above message and I don't 
>> know how to erase it.
>
> You can't, this is a mailing list not a forum.
>
>> The following post is the complete one:
>>
>> Given the following code:
>>
>> int[] arr = [1, 2, 9, 4, 10, 6];
>> auto r    = sort(arr);
>>
>> if(is(typeof(r) == SortedRange!(int[], "a<b")))
>>     writeln("first if");
>>
>> if(is(typeof(r) == SortedRange!(int[], "a < b")))
>>     writeln("second if");
>>
>> The program outputs only "second if". I assumed that it should 
>> have printed both
>> ifs. Is this a bug?
>>
>
> equality of lambdas are fickle. String lambdas are comparable, 
> because strings are comparable. Comparison of 
> `(args){...body...}`  or `() => expression` lambdas don't work 
> at all in template expressions.
>
> `SortedRange!(int[], "a<b") == SortedRange!(int[], "a < b")` is 
> false because the arguments to the templates differ i.e. "a<b" 
> != "a < b".
>
> Is this a bug? no. is it weird, confusing and unintuitive? yes.

I think that lambda comparison should be done logically (by that 
I mean: what the function actually computes) not literally. For 
example: it is a mistake to consider the 2 two lambda functions 
different just because one expression has more white spaces. Also 
"a < b" is the same lambda function as "e < d"; considering these 
2 functions to not be equal is a mistake.