Re: alias to function literal, call without () not possible

[ag0aep6g via Digitalmars-d-learn]

On 08/03/2016 09:40 PM, Andre Pany wrote:

Thanks for the info. Yes, I forgot the () for new Object;
Adding the () for new Object() still returns the same error.


`new Object` without parentheses is perfectly fine.

Re: alias to function literal, call without () not possible

[Kagamin via Digitalmars-d-learn]

Function pointers and delegates are not intended to allow 
optional parentheses. See also DIP23.

Re: alias to function literal, call without () not possible

[Andre Pany via Digitalmars-d-learn]

On Wednesday, 3 August 2016 at 18:15:23 UTC, Anonymouse wrote:

On Wednesday, 3 August 2016 at 17:16:10 UTC, Andre Pany wrote:

[...]



[...]
...is an alias for a delegate/function returning an Object. It 
is analogous to

[...]



[...]
...is a function accepting an Object parameter. In main you are 
trying to call this overload

[...]

...which is essentially

[...]


You can use pragma(msg, typeof(symbol).stringof) to inspect 
what types are being thrown around.

[...]


You could argue that parameterless function call rules should 
apply here and have it implicitly converted to bar(foo()), but 
it doesn't. I imagine the ambiguity (of delegate vs function 
return value) would just cause more problems than it would 
solve.


Thanks for the info. Yes, I forgot the () for new Object;
Adding the () for new Object() still returns the same error.
I think you are right with the ambiguity.

Kind regards
André

Re: alias to function literal, call without () not possible

[Anonymouse via Digitalmars-d-learn]

On Wednesday, 3 August 2016 at 17:16:10 UTC, Andre Pany wrote:

Hi,

I just stumbled over this behavior. I am not sure whether
the behavior is correct or not.
[...]



alias foo = () => new Object;
...is an alias for a delegate/function returning an Object. It is 
analogous to

alias foo = () { return new Object; };



void bar(Object o){}
...is a function accepting an Object parameter. In main you are 
trying to call this overload

void bar(Object function() o){}

...which is essentially

void bar(typeof(foo) o) {}


You can use pragma(msg, typeof(symbol).stringof) to inspect what 
types are being thrown around.

void bar(T)(T t)
{
pragma(msg, T.stringof); // "Object function() pure nothrow 
@safe"

}

void main()
{
auto n1 = foo;
pragma(msg, typeof(foo).stringof); // "Object function() 
pure nothrow @safe"

bar(foo);
}


You could argue that parameterless function call rules should 
apply here and have it implicitly converted to bar(foo()), but it 
doesn't. I imagine the ambiguity (of delegate vs function return 
value) would just cause more problems than it would solve.

alias to function literal, call without () not possible

[Andre Pany via Digitalmars-d-learn]

Hi,

I just stumbled over this behavior. I am not sure whether
the behavior is correct or not.

alias foo = () => new Object;
void bar(Object o){}

void main()
{
auto n1 = foo;
bar(foo);
}

While first line in main is working fine,
second line does not compile due to missing ().

Is this correct?

Kind regards
André