sortUniq

[zeljkog via Digitalmars-d]

On 24.01.15 15:53, Andrei Alexandrescu wrote:
> On 1/24/15 4:13 AM, zeljkog wrote:
>> On 24.01.15 12:50, Peter Alexander wrote:
>>> auto f = unique();
>>> [1, 5, 5, 2, 1, 5, 6, 6].filter!(f).writeln;  // [1, 5, 2, 6]
>>>
>>> Filter needs an alias, and you cannot alias an R-value (it has no
>>> symbol).
>>
>> Yes, I see :)
>>
>> But I think this should be supported by std.algorithm:
>>
>> import std.stdio, std.algorithm;
>>
>> struct Uniq{
>>      bool[int] c;
>>      bool opCall(int a){
>>          if (a in c)
>>              return false;
>>          else{
>>              c[a] = true;
>>              return true;
>>          }
>>      }
>> }
>>
>> void main()
>> {
>>      [1, 5, 5, 2, 1, 5, 6, 6].filter!Uniq.writeln;
>> }
>
> I can't make sense of this - where is Uniq supposed to be instantiated?
> -- Andrei
>

Require following changes in std.algorithm.filter.

original:

template filter(alias predicate) if (is(typeof(unaryFun!predicate)))
{
     auto filter(Range)(Range range) if (isInputRange!(Unqual!Range))
     {
         return FilterResult!(unaryFun!predicate, Range)(range);
     }
}

private struct FilterResult(alias pred, Range)
...

changed (to run this case):

template filter(alias predicate) if (is(typeof(unaryFun!predicate)))
{
     auto filter(Range)(Range range) if (isInputRange!(Unqual!Range))
     {
         static if (is(predicate == struct))
             return FilterResult!(predicate, Range)(range);
         else
             return FilterResult!(unaryFun!predicate, Range)(range);
     }
}

private struct FilterResult(alias predicate, Range)
{
     static if (is(predicate == struct))
         predicate pred;
     else
         alias pred = predicate;
...