Comparators.comparing overloads

[Sam Pullara]

I'm not even sure it is just the boxed/unboxed. The error message indicates it is confused with the long and double version as well.

Sam

On Jul 21, 2013, at 2:40 PM, Ali Ebrahimi <ali.ebrahimi1781 at gmail.com> wrote:

> Hi,
> if we make compiler smarter and always primitives functional descriptors
> wins over boxed (& Refference)
> functional descriptors in that case we can disambiguate this case. With
> this approach we don't need to mangle method names(just one map with
> overloads).
> 
> 
> On Mon, Jul 22, 2013 at 1:46 AM, Richard Warburton <
> richard.warburton at gmail.com> wrote:
> 
>> Hi,
>> 
>> We only mangle the name for return types, not argument types.
>>> 
>> 
>> Thanks for the prompt reply.
>> 
>> Things still seem a little messy in this situation though.  Perhaps I've
>> missed something but we're talking about needing a cast for
>> any keyExtractor function that returns a number.  That seems to be a fairly
>> common scenario for a keyExtractor.  Suppose I want to sort Strings by
>> length, and I want to write:
>> 
>> Comparator<String> comparator = comparing(String::length);
>> 
>> I'll get an error telling me that the "reference to comparing is
>> ambiguous".  Now in fact I can't even hint to the compiler using a return
>> type cast as with the following snippet:
>> 
>> Comparator<String> comparator = comparing(str -> (int) str.length());
>> 
>> I presume this is because a cast to int can auto-box to Integer which
>> subtypes Object, so its still ambiguous between Function and ToIntFunction.
>> Again, perhaps I've missed something here, but the way to get around this
>> issue is by providing an explicit type for the keyExtractor function:
>> 
>> ToIntFunction<String> lengthOfString = String::length;
>> Comparator<String> comparator = comparing(lengthOfString);
>> 
>> Which really does seem less elegant to me than having overloads with
>> mangled names. As I say this isn't a weird corner case - numbers are an
>> obvious thing to use as a comparator key.
>> 
>> regards,
>> 
>>  Dr. Richard Warburton
>> 
>>  http://insightfullogic.com
>>  @RichardWarburto <http://twitter.com/richardwarburto>
>> 
>> 
>