Hi,

I just noticed ufcs does not work with alias. Is this limitation needed?

void foo(int a) {}

void main()
{
	alias bar = foo;
	3.foo();
	3.bar();
}

Last line fails  with "no property 'bar' for type int.

Should I open an enhancement request?

Kind regards
André

On 07/09/2016 8:06 PM, Andre Pany wrote:
>
> Should I open an enhancement request?

No.
It works outside of the function (part of lookup rules).

On Wednesday, 7 September 2016 at 08:08:34 UTC, rikki cattermole wrote:
> On 07/09/2016 8:06 PM, Andre Pany wrote:
>>
>> Should I open an enhancement request?
>
> No.
> It works outside of the function (part of lookup rules).

I simplified my example too much. Yes in the example above I can move the alias
outside the main function. Here is a more complex example.

As I use the input parameter args in the alias, I cannot move the alias outside
the main function.

import std.algorithm;
bool fulfillsKeyPredicate(string s, string t) {return true;}

void main(string[] args)
{
	alias keyPredicateFilter = filter!(e => e.fulfillsKeyPredicate(args[0]));
	string[] arr;
	
	keyPredicateFilter(arr);
	arr.keyPredicateFilter;
}

Is there a workaround? Or is still a valid scenario to change the lookup rules?

Kind regards
André

On 07/09/2016 8:26 PM, Andre Pany wrote:
> On Wednesday, 7 September 2016 at 08:08:34 UTC, rikki cattermole wrote:
>> On 07/09/2016 8:06 PM, Andre Pany wrote:
>>>
>>> Should I open an enhancement request?
>>
>> No.
>> It works outside of the function (part of lookup rules).
>
> I simplified my example too much. Yes in the example above I can move
> the alias
> outside the main function. Here is a more complex example.
>
> As I use the input parameter args in the alias, I cannot move the alias
> outside
> the main function.
>
> import std.algorithm;
> bool fulfillsKeyPredicate(string s, string t) {return true;}
>
> void main(string[] args)
> {
>     alias keyPredicateFilter = filter!(e =>
> e.fulfillsKeyPredicate(args[0]));
>     string[] arr;
>
>     keyPredicateFilter(arr);
>     arr.keyPredicateFilter;
> }
>
> Is there a workaround? Or is still a valid scenario to change the lookup
> rules?

People have tried, this is the behavior as designed.

The workaround is simple, don't use UFCS.

I won't repeat the explanation or reasoning here, plenty of posts on it ;)

On Wednesday, 7 September 2016 at 08:35:26 UTC, rikki cattermole wrote:
> On 07/09/2016 8:26 PM, Andre Pany wrote:
>> [...]
>
> People have tried, this is the behavior as designed.
>
> The workaround is simple, don't use UFCS.
>
> I won't repeat the explanation or reasoning here, plenty of posts on it ;)

Thanks, this answer my question.

Kind regards
André

On 9/7/16 4:26 AM, Andre Pany wrote:
> On Wednesday, 7 September 2016 at 08:08:34 UTC, rikki cattermole wrote:
>> On 07/09/2016 8:06 PM, Andre Pany wrote:
>>>
>>> Should I open an enhancement request?
>>
>> No.
>> It works outside of the function (part of lookup rules).
>
> I simplified my example too much. Yes in the example above I can move
> the alias
> outside the main function. Here is a more complex example.
>
> As I use the input parameter args in the alias, I cannot move the alias
> outside
> the main function.
>
> import std.algorithm;
> bool fulfillsKeyPredicate(string s, string t) {return true;}
>
> void main(string[] args)
> {
>     alias keyPredicateFilter = filter!(e =>
> e.fulfillsKeyPredicate(args[0]));
>     string[] arr;
>
>     keyPredicateFilter(arr);
>     arr.keyPredicateFilter;
> }
>
> Is there a workaround? Or is still a valid scenario to change the lookup
> rules?

There is a workaround, identified by Vladimir Panteleev (https://blog.thecybershadow.net/2015/04/28/the-amazing-template-that-does-nothing/):


import std.algorithm;
bool fulfillsKeyPredicate(string s, string t) {return true;}

alias I(alias x) = x;

void main(string[] args)
{
    alias keyPredicateFilter = filter!(e => e.fulfillsKeyPredicate(args[0]));
    string[] arr;

    keyPredicateFilter(arr);
    arr.I!keyPredicateFilter;
}

Unfortunately, you can't alias the I!someSymbol, as that has the same problem.

-Steve

On Thursday, 8 September 2016 at 13:38:54 UTC, Steven Schveighoffer wrote:
>
> There is a workaround, identified by Vladimir Panteleev (https://blog.thecybershadow.net/2015/04/28/the-amazing-template-that-does-nothing/):
>
>
> import std.algorithm;
> bool fulfillsKeyPredicate(string s, string t) {return true;}
>
> alias I(alias x) = x;
>
> void main(string[] args)
> {
>     alias keyPredicateFilter = filter!(e => e.fulfillsKeyPredicate(args[0]));
>     string[] arr;
>
>     keyPredicateFilter(arr);
>     arr.I!keyPredicateFilter;
> }
>
> Unfortunately, you can't alias the I!someSymbol, as that has the same problem.
>
> -Steve

Thanks for this insight. In my case I prepare a presentation about D
(audience doesn't now anything about D)
and tried to make my D code as beautiful as possible. As solution
I created now a free template method and hide it in a library module.

T[] filterByKeyPredicate(T)(T[] arr, string[string] keyPredicate)
{
...filter!....
}

This way I can use UFCS.

Kind regards
André