int delegate(int) dg = (i) => i * 2;

Error: non-constant nested delegate literal expression __lambda3


int delegate(int) dg;

static this() {
   dg = i => i * 2; // ok
}


Am I doing anything wrong?

Atila

On Friday, 25 March 2016 at 20:54:28 UTC, Atila Neves wrote:
> int delegate(int) dg = (i) => i * 2;
>
> Error: non-constant nested delegate literal expression __lambda3
>
>
> int delegate(int) dg;
>
> static this() {
>    dg = i => i * 2; // ok
> }
>
>
> Am I doing anything wrong?
>
> Atila

Hmm, looks like your first delegate is a function type and the second is a function instance. So the first version written like this ...

import std.stdio;

alias dg = int delegate(int);

dg make_dg(){
	return i => i*2;
}

void main(){
	auto my_dg = make_dg();
	writeln(my_dg(3));
}

will work.

On Friday, 25 March 2016 at 23:40:37 UTC, data pulverizer wrote:
> On Friday, 25 March 2016 at 20:54:28 UTC, Atila Neves wrote:
>> int delegate(int) dg = (i) => i * 2;
>>
>> Error: non-constant nested delegate literal expression __lambda3
>>
>>
>> int delegate(int) dg;
>>
>> static this() {
>>    dg = i => i * 2; // ok
>> }
>>
>>
>> Am I doing anything wrong?
>>
>> Atila
>
> Hmm, looks like your first delegate is a function type and the second is a function instance. So the first version written like this ...
>
> import std.stdio;
>
> alias dg = int delegate(int);
>
> dg make_dg(){
> 	return i => i*2;
> }
>
> void main(){
> 	auto my_dg = make_dg();
> 	writeln(my_dg(3));
> }
>
> will work.

In fact for the second case I'd probably need to see a working struct/class prototype to make a firm comment on it.